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>

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>
Stephen Warren · Tom Rini
1 parent e736570cc3
Showing 1 changed file with 16 additions and 0 deletions Side-by-side Diff
include/config_distro_bootcmd.h
@@ -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
...	...	@@ -10,6 +10,22 @@
10	10	#ifndef _CONFIG_CMD_DISTRO_BOOTCMD_H
11	11	#define _CONFIG_CMD_DISTRO_BOOTCMD_H
12	12
	13	+/*
	14	+ * A note on error handling: It is possible for BOOT_TARGET_DEVICES to
	15	+ * reference a device that is not enabled in the U-Boot configuration, e.g.
	16	+ * it may include MMC in the list without CONFIG_CMD_MMC being enabled. Given
	17	+ * that BOOT_TARGET_DEVICES is a macro that's expanded by the C pre-processor
	18	+ * at compile time, it's not possible to detect and report such problems via
	19	+ * a simple #ifdef/#error combination. Still, the code needs to report errors.
	20	+ * The best way I've found to do this is to make BOOT_TARGET_DEVICES expand to
	21	+ * reference a non-existent symbol, and have the name of that symbol encode
	22	+ * the error message. Consequently, this file contains references to e.g.
	23	+ * BOOT_TARGET_DEVICES_references_MMC_without_CONFIG_CMD_MMC. Given the
	24	+ * prevalence of capitals here, this looks like a pre-processor macro and
	25	+ * hence seems like it should be all capitals, but it's really an error
	26	+ * message that includes some other pre-processor symbols in the text.
	27	+ */
	28	+
13	29	/* We need the part command */
14	30	#define CONFIG_PARTITION_UUIDS
15	31	#define CONFIG_CMD_PART