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Standardise usage of rom_get_sys_info function #3094

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Standardise usage of rom_get_sys_info function #3094

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6 changes: 3 additions & 3 deletions src/rp2_common/pico_bootrom/bootrom.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,8 +86,8 @@ void __attribute__((noreturn)) rom_reset_usb_boot_extra(int usb_activity_gpio_pi
#if !PICO_RP2040
bool rom_get_boot_random(uint32_t out[4]) {
uint32_t result[5];
rom_get_sys_info_fn func = (rom_get_sys_info_fn) rom_func_lookup_inline(ROM_FUNC_GET_SYS_INFO);
if (5 == func(result, count_of(result), SYS_INFO_BOOT_RANDOM)) {
int words_returned = rom_get_sys_info(result, 5, SYS_INFO_BOOT_RANDOM);

@will-v-pi will-v-pi Jul 23, 2026

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I think using count_of might be clearer - and then the uses in bootrom.h could be updated to count_of too

Suggested change
int words_returned = rom_get_sys_info(result, 5, SYS_INFO_BOOT_RANDOM);
int words_returned = rom_get_sys_info(result, count_of(result), SYS_INFO_BOOT_RANDOM);

@lurch lurch Jul 23, 2026

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Okay, I can change all of these. Is it still appropriate for count_of to continue being used in the words_returned == count_of(result) check on the next line too? This would mean that the number 5 only appears in the uint32_t result[5] line. (Which would be fine with me, I'm always happy to see the elimination of duplicated magic-numbers; I'm just double-checking that this is what's desired.)

And in that case I guess it might make sense to fold #3089 into this PR too.

@will-v-pi will-v-pi Jul 23, 2026

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I think it's still appropriate - I also agree it's nice to remove the magic numbers.

Re folding the PRs, I don't mind - you could make the changes to use count_of in the existing bootrom.h functions in that PR, or fold it into this one and do it here

@lurch lurch Jul 23, 2026

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Taking that idea of removing magic-numbers even further, perhaps it would also make sense to add e.g.

#define SYS_INFO_BOOT_RANDOM_WORDS_RETURNED     _u(4)

to bootrom_constants.h, and then we could do

uint32_t result[SYS_INFO_BOOT_RANDOM_WORDS_RETURNED + 1];

?

@will-v-pi will-v-pi Jul 23, 2026

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Yeah, that sounds good too - for all the SYS_INFO_XXX defines having a corresponding SYS_INFO_XXX_WORDS_RETURNED rather than just having it in the comment above.

if (words_returned == count_of(result) && result[0] == SYS_INFO_BOOT_RANDOM) {
for(uint i=0;i<4;i++) {
out[i] = result[i+1];
}
Expand Down Expand Up @@ -209,4 +209,4 @@ int rom_pick_ab_partition_during_update(uint32_t *workarea_base, uint32_t workar

return rc;
}
#endif
#endif
33 changes: 22 additions & 11 deletions src/rp2_common/pico_unique_id/unique_id.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,12 @@
#include "pico/bootrom.h"
#include "pico/unique_id.h"

static_assert(PICO_UNIQUE_BOARD_ID_SIZE_BYTES <= FLASH_UNIQUE_ID_SIZE_BYTES, "Board ID size must at least be the size of flash ID");
#if PICO_RP2040
static_assert(PICO_UNIQUE_BOARD_ID_SIZE_BYTES <= FLASH_UNIQUE_ID_SIZE_BYTES, "Board ID size cannot be greater than the size of flash ID");
#else
#define SYS_INFO_DEVICE_ID_SIZE_BYTES 8
static_assert(PICO_UNIQUE_BOARD_ID_SIZE_BYTES <= SYS_INFO_DEVICE_ID_SIZE_BYTES, "Board ID size cannot be greater than the size of device ID");
#endif

static pico_unique_board_id_t retrieved_id;

Expand Down Expand Up @@ -38,16 +43,22 @@ static void __attribute__((PICO_UNIQUE_BOARD_ID_INIT_ATTRIBUTES)) _retrieve_uniq
#error unique board ID size is greater than flash unique ID size
#endif
#else
rom_get_sys_info_fn func = (rom_get_sys_info_fn) rom_func_lookup(ROM_FUNC_GET_SYS_INFO);
union {
uint32_t words[9];
uint8_t bytes[9 * 4];
} out;
__unused int rc = func(out.words, 9, SYS_INFO_CHIP_INFO);
assert(rc == 4);
for (int i = 0; i < PICO_UNIQUE_BOARD_ID_SIZE_BYTES; i++) {
retrieved_id.id[i] = out.bytes[PICO_UNIQUE_BOARD_ID_SIZE_BYTES - 1 + 2 * 4 - i];
}
#if PICO_UNIQUE_BOARD_ID_SIZE_BYTES <= SYS_INFO_DEVICE_ID_SIZE_BYTES
union {
uint32_t words[4];
uint8_t bytes[4 * 4];
} out;
int words_returned = rom_get_sys_info(out.words, 4, SYS_INFO_CHIP_INFO);

@will-v-pi will-v-pi Jul 23, 2026

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Ditto on count_of

Suggested change
int words_returned = rom_get_sys_info(out.words, 4, SYS_INFO_CHIP_INFO);
int words_returned = rom_get_sys_info(out.words, count_of(out.words), SYS_INFO_CHIP_INFO);

assert(words_returned == 4);
if (words_returned == count_of(out.words) && out.words[0] == SYS_INFO_CHIP_INFO) {
for (int i = 0; i < PICO_UNIQUE_BOARD_ID_SIZE_BYTES; i++) {
// The device ID is in words 3 and 4, so skip the first two words (i.e. the first 8 bytes)
retrieved_id.id[i] = out.bytes[PICO_UNIQUE_BOARD_ID_SIZE_BYTES - 1 + 2 * 4 - i];
}
}
#else
#error unique board ID size is greater than device unique ID size
#endif
#endif
}

Expand Down
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