config_distro_bootcmd.h: add note on error handling

This should make it more clear why there appear to be C pre-processor
symbols in the file that contain mixed case. They're really error
messages.

Suggested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Stephen Warren 2015-03-10 15:40:58 -06:00 committed by Tom Rini
parent e736570cc3
commit 90b7caaf55

View file

@ -10,6 +10,22 @@
#ifndef _CONFIG_CMD_DISTRO_BOOTCMD_H
#define _CONFIG_CMD_DISTRO_BOOTCMD_H
/*
* A note on error handling: It is possible for BOOT_TARGET_DEVICES to
* reference a device that is not enabled in the U-Boot configuration, e.g.
* it may include MMC in the list without CONFIG_CMD_MMC being enabled. Given
* that BOOT_TARGET_DEVICES is a macro that's expanded by the C pre-processor
* at compile time, it's not possible to detect and report such problems via
* a simple #ifdef/#error combination. Still, the code needs to report errors.
* The best way I've found to do this is to make BOOT_TARGET_DEVICES expand to
* reference a non-existent symbol, and have the name of that symbol encode
* the error message. Consequently, this file contains references to e.g.
* BOOT_TARGET_DEVICES_references_MMC_without_CONFIG_CMD_MMC. Given the
* prevalence of capitals here, this looks like a pre-processor macro and
* hence seems like it should be all capitals, but it's really an error
* message that includes some other pre-processor symbols in the text.
*/
/* We need the part command */
#define CONFIG_PARTITION_UUIDS
#define CONFIG_CMD_PART