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dm: blk: Add comments to a few functions
The block interface is not well documented in the code. Pick two important functions and add comments. Signed-off-by: Simon Glass <sjg@chromium.org> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Tested-by: Stephen Warren <swarren@nvidia.com>
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@ -53,12 +53,42 @@ typedef struct disk_partition {
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/* Misc _get_dev functions */
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#ifdef CONFIG_PARTITIONS
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/**
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* get_dev() - get a pointer to a block device given its type and number
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*
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* Each interface allocates its own devices and typically struct blk_desc is
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* contained with the interface's data structure. There is no global
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* numbering for block devices, so the interface name must be provided.
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*
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* @ifname: Interface name (e.g. "ide", "scsi")
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* @dev: Device number (0 for first device on that interface, 1 for
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* second, etc.
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* @return pointer to the block device, or NULL if not available, or an
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* error occurred.
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*/
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struct blk_desc *get_dev(const char *ifname, int dev);
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struct blk_desc *ide_get_dev(int dev);
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struct blk_desc *sata_get_dev(int dev);
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struct blk_desc *scsi_get_dev(int dev);
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struct blk_desc *usb_stor_get_dev(int dev);
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struct blk_desc *mmc_get_dev(int dev);
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/**
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* mmc_select_hwpart() - Select the MMC hardware partiion on an MMC device
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*
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* MMC devices can support partitioning at the hardware level. This is quite
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* separate from the normal idea of software-based partitions. MMC hardware
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* partitions must be explicitly selected. Once selected only the region of
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* the device covered by that partition is accessible.
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*
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* The MMC standard provides for two boot partitions (numbered 1 and 2),
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* rpmb (3), and up to 4 addition general-purpose partitions (4-7).
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*
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* @dev_num: Block device number (struct blk_desc->dev value)
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* @hwpart: Hardware partition number to select. 0 means the raw device,
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* 1 is the first partition, 2 is the second, etc.
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* @return 0 if OK, other value for an error
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*/
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int mmc_select_hwpart(int dev_num, int hwpart);
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struct blk_desc *systemace_get_dev(int dev);
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struct blk_desc *mg_disk_get_dev(int dev);
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