Commit graph

40 commits

Author SHA1 Message Date
Ramon Fried
30b3241368 usb:ci_udc: don't overwrite configuration on pullup
change writel to writebits32 in ci_pullup() in order
to keep phy configuration in tact.

Signed-off-by: Ramon Fried <ramon.fried@gmail.com>
2018-09-30 13:00:37 -04:00
Ramon Fried
816495299d usb:ci_udc: Introduce init_after_reset phy function
MSM variant of Chipidea must reinitalize the phy
after controller reset.
Introduce ci_init_after_reset() weak function that
can be used to achieve the above init.

Signed-off-by: Ramon Fried <ramon.fried@gmail.com>
2018-09-30 13:00:36 -04:00
Tom Rini
83d290c56f SPDX: Convert all of our single license tags to Linux Kernel style
When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from.  So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry.  Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.

In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.

This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents.  There's also a few places where I found we did not have a tag
and have introduced one.

Signed-off-by: Tom Rini <trini@konsulko.com>
2018-05-07 09:34:12 -04:00
Masahiro Yamada
1221ce459d treewide: replace #include <asm/errno.h> with <linux/errno.h>
Now, arch/${ARCH}/include/asm/errno.h and include/linux/errno.h have
the same content.  (both just wrap <asm-generic/errno.h>)

Replace all include directives for <asm/errno.h> with <linux/errno.h>.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
[trini: Fixup include/clk.]
Signed-off-by: Tom Rini <trini@konsulko.com>
2016-09-23 17:55:42 -04:00
Ye.Li
8991fdef6d usb:ci_udc: Remove ULPI setting for i.MX OTG controller
All the i.MX6, i.MX23 and i.MX28 OTG controllers only support UTMI
interface. Set to ULPI is not correct, even the controller will
reject this setting in PORTSC register.

Signed-off-by: Ye.Li <B37916@freescale.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
2016-01-16 07:06:55 +01:00
Stephen Warren
b337b3b2a5 usb: ci_udc: fix emissions of ZLPs
Commit 6a13241635 "ci_udc: Update the ci_udc driver to support bulk
transfers" caused the value of "len" to change without updating subsquent
users of that variable in ci_ep_submit_next_request(). This caused the
code that detects when to emit ZLPs (Zero Length Packets) never to
trigger, which in turn caused host timeouts when a ZLP was required,
which in turn broke tests/dfu/, even despite the assertion in that
commit's description that "These changes are tested for both the DFU and
lthor."

Fix this by modifying the added dtd iteration code not to modify "len",
but rather to keep state in a separate variable. Rename the variables
while we're at it so they describe their purpose better.

Fixes: 6a13241635 ("ci_udc: Update the ci_udc driver to support bulk transfers")
Cc: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
2015-09-12 20:24:42 +02:00
Peng Fan
70eaeb03c1 usb: gadget: ci_udc: implement usb_ep_ops dequeue callback
Implement endpoint dequeue callback function.

Without this function, uboot will hang when executing fastboot comamnd.
See following flow:
"fastboot_tx_write_str->fastboot_tx_write->usb_ep_dequeue->ep->ops->dequeue"
without implement ci_udc dequeue function, ep->ops->dequeue is NULL, then
uboot will hang.

Tested on mx6qsabresd board with fastboot enabled.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Cc: "Łukasz Majewski" <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
2015-09-12 20:24:42 +02:00
Rob Herring
58d6d139c3 usb: ci_udc: fix request allocation when endpoints are disabled
The ci_udc driver request allocation assumes that the endpoint descriptor
pointer is set to retrieve the endpoint number, but that is only true
when the endpoint is enabled. This results in a NULL ptr dereference
which for me happens to return 0 value. This causes the EP0 request
struct to be returned for other endpoints. Some gadget drivers like
fastboot and USB MS work fine, but ethernet does not.

Really, the ci_udc driver is the oddball here doing this EP0 special
case handling Stephen added. All the other drivers alloc/free functions
are pretty much the same with the only variation being the size of the
private struct. This could all be consolidated to a common function.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Marek Vasut <marex@denx.de>
Acked-by: Stephen Warren <swarren@nvidia.com>
2015-07-24 22:08:38 +02:00
Stephen Warren
85a9ea314e ci_udc: fix 64-bit compile warnings
This is the same as f72d8320b6 "usb: ci_udc: fix warnings on 64-bit
builds", but more.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2015-07-23 09:00:08 +02:00
Siva Durga Prasad Paladugu
6a13241635 ci_udc: Update the ci_udc driver to support bulk transfers
Update the ci_udc driver to support bulk transfer
and also added capability of having multiple dtds
if requested data is more than 16K.
These changes are tested for both the DFU and lthor.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
2015-05-29 12:41:04 +02:00
Simon Glass
fbeceb2602 dm: usb: Allow setting up a USB controller as a device/gadget
Some controllers support OTG (on-the-go) where they can operate as either
host or device. The gadget layer in U-Boot supports this.

While this layer does not interact with driver model, we can provide a
function which sets up the controller in the correct way. This way the code
at least builds (although it likely will not work).

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
2015-04-18 11:11:25 -06:00
Kishon Vijay Abraham I
2d48aa69bd usb: modify usb_gadget_handle_interrupts to take controller index
Since we support multiple dwc3 controllers to be existent at the same
time, in order to handle the interrupts of a particular dwc3 controller
usb_gadget_handle_interrutps should take controller index as an
argument.

Hence the API of usb_gadget_handle_interrupts is modified to take
controller index as an argument and made the corresponding changes to all
the usb_gadget_handle_interrupts calls.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
2015-04-14 05:48:11 +02:00
Rob Herring
f72d8320b6 usb: ci_udc: fix warnings on 64-bit builds
Change addresses to unsigned long to be compatible with 64-bit builds.
Regardless of fixing warnings, the device is still only 32-bit capable.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: "Łukasz Majewski" <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
2015-04-14 05:47:47 +02:00
Eric Nelson
e206799370 usb: ci_udc: respect CONFIG_USB_GADGET_DUALSPEED
Force full-speed (12 Mbit/s) operation if CONFIG_USB_GADGET_DUALSPEED
is not defined.

The controller is capable of high-speed (480 Mbit/s) operation,
but some designs may require the use of lower-speed operation.

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
2014-10-06 14:50:44 +02:00
Stephen Warren
842ef9a98e usb: ci_udc: implement dfu_usb_get_reset
This allows the USB code to determine whether a USB bus reset was issued,
which in turn allows the code to differentiate between a detach (return
to shell prompt) and a board reset/reboot request.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-09-02 14:29:28 +02:00
Stephen Warren
dcb89b5aa0 usb: ci_udc: use var name ep/ci_ep consistently
Almost all of ci_udc.c uses variable name "ep" for a struct usb_ep and
"ci_ep" for a struct ci_ep. This is nice and consistent, and helps people
know what type a variable is without searching for the declaration.
handle_ep_complete() doesn't do this, so fix it to be consistent.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
639e9903c2 usb: ci_udc: don't memalign() struct ci_req allocations
struct ci_req is a purely software structure, and needs no specific
memory alignment. Hence, allocate it with calloc() rather than
memalign(). The use of memalign() was left-over from when struct ci_req
was going to hold the aligned bounce buffer, but this is now dynamically
allocated.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
6ac15fda4e usb: ci_udc: remove controller.items array
There's no need to store an array of QTD pointers in the controller.
Since the calculation is so simple, just have ci_get_qtd() perform it
at run-time, rather than pre-calculating everything.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
7e54188775 usb: ci_udc: fix items array size/stride calculation
2 QTDs are allocated for each EP. The current allocation scheme aligns
the first QTD in each pair, but simply adds the struct size to calculate
the second QTD's address. This will result in a non-cache-aligned
addresss IF the system's ARCH_DMA_MINALIGN is not 32 bytes (i.e. the
size of struct ept_queue_item).

Similarly, the original ilist_ent_sz calculation aligned the value to
ARCH_DMA_MINALIGN but didn't take the USB HW's 32-byte alignment
requirement into account. This doesn't cause a practical issue unless
ARCH_DMA_MINALIGN < 32 (which I suspect is quite unlikely), but we may
as well fix the code to be explicit, so it's obviously completely
correct.

The new value of ILIST_ENT_SZ takes all alignment requirements into
account, so we can simplify ci_{flush,invalidate}_qtd() by simply using
that macro rather than calling roundup().

Similarly, the calculation of controller.items[i] can be simplified,
since each QTD is evenly spaced at its individual alignment requirement,
rather than each pair being aligned, and entries within the pair being
spaced apart only by structure size.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
06b38fcbae usb: ci_udc: lift ilist size calculations to global scope
This will allow functions other than ci_udc_probe() to make use of the
constants in a future change.

This in turn requires converting the const int variables to #defines,
since the initialization of one global const int can't depend on the
value of another const int; the compiler thinks it's non-constant if
that dependency exists.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
8d7c39d3e8 usb: ci_udc: don't assume QTDs are adjacent when transmitting ZLPs
Fix ci_ep_submit_next_request()'s ZLP transmission code to explicitly
call ci_get_qtd() to find the address of the other QTD to use. This
will allow us to correctly align each QTD individually in the future,
which may involve leaving a gap between the QTDs.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
d7beeb9358 usb: ci_udc: fix ci_flush_{qh,qtd} calls in ci_udc_probe()
ci_udc_probe() initializes a pair of QHs and QTDs for each EP. After
each pair has been initialized, the pair is cache-flushed. The
conversion from QH/QTD index [0..2*NUM_END_POINTS) to EP index
[0..NUM_ENDPOINTS] is incorrect; it simply subtracts 1 (which yields
the QH/QTD index of the first entry in the pair) rather than dividing
by two (which scales the range). Fix this.

On my system, this avoids cache debug prints due to requests to flush
unaligned ranges. This is caused because the flush calls happen before
the items[] array entries are initialized for all but EP0.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-07-02 15:45:38 +02:00
Stephen Warren
83c3750088 usb: ci_udc: fix typo in debug message
s/ot/to/

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-25 22:22:20 +02:00
Stephen Warren
fb22ae6c7e usb: ci_udc: fix interaction with CONFIG_USB_ETH_CDC
ci_udc.c's usb_gadget_unregister_driver() doesn't call driver->unbind()
unlike other USB gadget drivers. Fix it to do this.

Without this, when ether.c's CDC Ethernet device is torn down,
eth_unbind() is never called, so dev->gadget is never set to NULL.
For some reason, usb_eth_halt() is called both at the end of the first
use of the Ethernet device, and prior to any subsequent use. Since
dev->gadget is never cleared, all calls to usb_eth_halt() attempt to
stop, disconnect, and clean up the device, resulting in double cleanup,
which hangs U-Boot on my Tegra device at least.

ci_udc allocates its own singleton EP0 request object, and cleans it up
during usb_gadget_unregister_driver(). This appears necessary when using
the USB gadget framework in U-Boot, since that does not allocate/free
the EP0 request. However, the CDC Ethernet driver *does* allocate and
free its own EP0 requests. Consequently, we must protect
ci_ep_free_request() against double-freeing the request.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-25 22:22:20 +02:00
Stephen Warren
e0672b3c3a usb: ci_udc: terminate ep0 INs with a zlp when required
Sometimes, a zero-length packet is required at the end of an IN
transaction so that the host knows the device is done sending data.
Enhance ci_udc to send a zlp when necessary. See the comments for
more details.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-11 02:26:05 +02:00
Stephen Warren
b7c0051687 usb: ci_udc: clean up all allocations in unregister
usb_gadget_unregister_driver() is called to tear down the USB device mode
stack. Fix the driver to stop the USB HW (which causes any attached host
to notice the disappearance of the device), and free all allocations
(which obviously prevents memory leaks).

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-11 02:26:05 +02:00
Stephen Warren
9a7d34be13 usb: ci_udc: fix probe error cleanup
If allocation of the ep0 req fails, clean up all the allocations that
were made in ci_udc_probe().

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-11 02:26:05 +02:00
Stephen Warren
bdf81611e4 usb: ci_udc: fix freeing of ep0 req
ci_ep_alloc_request() avoids allocating multiple request objects for ep0
by keeping a record of the first req allocated for ep0, and always
returning that instead of allocating a new req. However, if this req is
ever freed, the record of the previous allocation is not cleared, so
ci_ep_alloc_request() will keep returning this stale pointer. Fix
ci_ep_free_request() to clear the record of the previous allocation.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-11 02:26:05 +02:00
Stephen Warren
43a8f25b6c usb: ci_udc: call udc_disconnect() from ci_pullup()
ci_pullup()'s !is_on path contains a cut/paste copy of udc_disconnect().
Remove the duplication by simply calling udc_disconnect() instead.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-11 02:26:05 +02:00
Stephen Warren
006c702688 usb: ci_udc: complete ep0 direction handling
handle_setup() currently assumes that the response to a Setup transaction
will be an OUT transaction, and any subsequent packet (if any) will be an
IN transaction. This appears to be valid in many cases; both USB
enumeration and Mass Storage work OK with this restriction. However, DFU
uses ep0 to transfer data in both directions. This renders the assumption
invalid; when sending data from device to host, the Data Stage is an IN
transaction, and the Status Stage is an OUT transaction. Enhance
handle_setup() to deduce the correct direction for the USB transactions
based on Setup transaction data.

ep0's request object only needs to be automatically re-queued when the
Data Stage completes, in order to implement the Status Stage. Once the
Status Stage transaction is complete, there is no need to re-queue the
USB request, so don't do that.

Don't sent USB request completion callbacks for Status Stage transactions.
These were queued by ci_udc itself, and only serve to confuse the USB
function code. For example, f_dfu attempts to interpret the 0-length data
buffers for Status Stage transactions as DFU packets. These buffers
contain stale data from the previous transaction. This causes f_dfu to
complain about a sequence number mismatch.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-01 19:22:40 +02:00
Stephen Warren
a2d8f92985 usb: ci_udc: pre-allocate ep0 req
Allocate ep0's USB request object when the UDC driver is probed. This
solves a couple of issues in the current code:

a) A request object always exists for ep0. Prior to this patch, if setup
transactions arrived in an unexpected order, handle_setup() would need
to reply to a setup transaction before any ep0 usb_req was created.

This issue was introduced in commit 2813006fec "usb: ci_udc: allow
multiple buffer allocs per ep."

b) handle_ep_complete no longer /has/ to queue the ep0 request again
after every single request completion. This is currently required, since
handle_setup() assumes it can find some request object in ep0's request
queue. This patch doesn't actually stop handle_ep_complete() from always
requeueing the request, but the next patch will.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-01 19:22:40 +02:00
Stephen Warren
054731b09e usb: ci_udc: use a single descriptor for ep0
ci_udc currently points ep->desc at separate descriptors for IN and OUT.
These descriptors only differ in the ep address IN/OUT field. Modify the
code to use a single descriptor, and change that descriptor's ep address
to indicate IN/OUT as required. This removes some data duplication.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-01 19:22:40 +02:00
Stephen Warren
7484d84cbb usb: ci_udc: detect queued requests on ep0
The flipping of ep0 between IN and OUT relies on ci_ep_queue() consuming
the current IN/OUT setting immediately. If this is deferred to a later
point when the req is pulled out of ci_req->queue, then the IN/OUT
setting may have been changed since the req was queued, and state will
get out of sync. This condition doesn't occur today, but could if bugs
were introduced later, and this error-check will save a lot of debugging
time.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-06-01 19:22:39 +02:00
Stephen Warren
8630c1c7e3 usb: ci_udc: parse QTD before over-writing it
ci_udc only allocates a single QTD structure per EP. All data needs to be
extracted from the DTD prior to calling ci_ep_submit_next_request(), since
that fills the QTD with next transaction's parameters. Fix
handle_ep_complete() to extract the transaction (remaining) length before
kicking off the next transaction.

In practice, this only causes writes to UMS devices to fail for me. I may
have tested the final versions of my previous ci_udc patch only with
reads. More recently, I had patches applied locally that allocated a QTD
per USB request rather than per USB EP, although since that doesn't give
any performance benefit, I'm dropping those.

Fixes: 2813006fec ("usb: ci_udc: allow multiple buffer allocs per ep")
Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-05-15 00:21:30 +02:00
Stephen Warren
2813006fec usb: ci_udc: allow multiple buffer allocs per ep
Modify ci_ep_alloc_request() to return a dynamically allocated request
object, rather than a singleton that's part of the endpoint. This
requires moving various state from the endpoint structure to the request
structure, since we need one copy per request.

The "fast bounce buffer" b_fast is removed by this change rather than
moved to the request object. Instead, we enhance the bounce buffer logic
in ci_bounce()/ci_debounce() to keep the bounce buffer around between
request submissions. This avoids the need to allocate an arbitrarily-
sized bounce buffer up-front, yet avoids incurring the allocation
overhead each time a request is submitted.

A future enhancement would be to actually submit multiple requests to HW
at once. The Linux driver shows that this is possible. That might improve
throughput (depending on the USB protocol in use), since USB could be
performing a transfer to one HW buffer in parallel with whatever SW
actions U-Boot performs on another buffer. However, I have not made this
change as part of this patch, in order to keep SW changes related to
buffer management separate from any change in the way the HW is
programmed.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-05-07 23:36:58 +02:00
Stephen Warren
fcf2ede190 usb: ci_udc: support variants with hostpc register
Tegra's USB controller appears to be a variant of the ChipIdea
controller; perhaps derived from it, or simply a different version of
the IP core to what U-Boot supports today.

In this variant, at least the following difference are present:
- Some registers are moved about.
- Setup transaction completion is reported in a separate 'epsetupstat'
  register, rather than in 'epstat' (which still exists, perhaps for
  other transaction types).
- USB connection speed is reported in a separate 'hostpc1_devlc'
  register, rather than 'portsc'.
- The registers used by ci_udc.c begin at offset 0x130 from the USB
  register base, rather than offset 0x140. However, this is handled
  by the associated EHCI controller driver, since the register address
  is stored in controller.ctrl->hcor.

Introduce define CONFIG_CI_UDC_HAS_HOSTPC to indicate which variant of
the controller should be supported. The "HAS_HOSTPC" part of this name
mirrors the similar "has_hostpc" field used by the Linux EHCI controller
core to represent the presence/absence of the hostpc1_devlc register.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-04-30 10:30:57 +02:00
Stephen Warren
0c51dc6db9 usb: ci_udc: make PHY initialization conditional
usb_gadget_register_driver() currently unconditionally programs PORTSC
to select a ULPI PHY. This is incorrect on at least the Tegra boards I
am testing with, which use a UTMI PHY for the OTG ports. Make the PHY
selection code conditional upon the specific EHCI controller that is in
use.

Ideally, I believe that the PHY initialization code should be part of
ehci_hcd_init() in the relevant EHCI controller driver, or some board-
specific function that ehci_hcd_init() calls.

For MX6, I'm not sure this PHY initialization code is correct even before
this patch, since ehci-mx6's ehci_hcd_init() already configures PORTSC to
a board-specific value, and it seems likely that the code in ci_udc.c is
incorrectly undoing this. Perhaps this is not an issue if the PHY
selection register bits aren't implemented on this instance of the MX6
USB controller?

ehci-mxs.c doens't appear to touch PORTSC, so this code is likely still
required there.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-04-30 10:30:57 +02:00
Stephen Warren
8aac6e9c53 usb: ci_udc: set ep->req.actual after transfer
At least drivers/usb/gadget/storage_common.c expects that ep->req.actual
contain the number of bytes actually transferred. (At least in practice,
I observed it failing to work correctly unless this was the case).

However, ci_udc.c modifies ep->req.length instead. I assume that .length
 is supposed to represent the allocated buffer size, whereas .actual is
supposed to represent the actual number of bytes transferred. In the OUT
transaction case, this may happen simply because the host sends a smaller
 packet than the max possible size, which is quite legal. In the IN case,
transferring fewer bytes than requested could presumably happen as an
error.

Modify handle_ep_complete() to write to .actual rather than modifying
.length.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-04-30 10:30:57 +02:00
Stephen Warren
f5c03006dd usb: ci_udc: Support larger packets
ci_ep_queue() currently only fills in the page0/page1 fields in the
queue item. If the buffer is larger than 4KiB (unaligned) or 8KiB
(page-aligned), then this prevents the HW from knowing where to write
the balance of the data.

Fix this by initializing all 5 pageN pointers, which allows up to
16KiB (potentially non-page-aligned) buffers.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
2014-04-30 10:30:57 +02:00
Marek Vasut
f016f8ca3d usb: mv_udc: Rename to ci_udc
The mv_udc is not marvell-specific anymore. The mv_udc is used to drive
generic ChipIdea CI13xxx series OTG cores, so rename the driver to ci_udc
instead.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Stefano Babic <sbabic@denx.de>
2014-02-06 04:48:15 +01:00
Renamed from drivers/usb/gadget/mv_udc.c (Browse further)