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sdcard: replace VLA with static buffer, add card presence guard #205

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Merged
bessman merged 2 commits into from
May 3, 2026
Merged

sdcard: replace VLA with static buffer, add card presence guard #205

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sdcard: replace VLA with static buffer, add card presence guard
dhruvmittal41 Apr 16, 2026
285d04e
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bessman May 3, 2026
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76 changes: 46 additions & 30 deletions src/sdcard/sdcard.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,16 +4,25 @@

#include "../bus/uart/uart.h"
#include "../commands.h"
#include "fatfs/ff.h"
#include "fatfs/ffconf.h"
#include "../helpers/debug.h"
#include "../registers/system/watchdog.h"
#include "fatfs/ff.h"
#include "fatfs/ffconf.h"
#include "sd_spi.h"

#define SFN_MAX 8
#define SFN_SUFFIX_LEN 4 // Period + at most three chars.
#define BUF_MAX FF_MIN_SS
#define SDCARD_DRIVE "0:"

static void get_filename(TCHAR* const fn_buf, UINT const size) {
static TCHAR s_sector_buf[BUF_MAX];
_Static_assert(
sizeof(s_sector_buf) == 512,
"SD sector buffer must be 512 bytes"
);
Comment on lines +19 to +23

static void get_filename(TCHAR *const fn_buf, UINT const size)
{
for (UINT i = 0; i < size; ++i) {
if (!(fn_buf[i] = UART1_Read())) {
Comment on lines +25 to 28
// Received null-terminator.
Expand All @@ -24,15 +33,20 @@ static void get_filename(TCHAR* const fn_buf, UINT const size) {
// manual check for null-termination.
}

response_t SDCARD_write_file(void) {
response_t SDCARD_write_file(void)
{
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// +1 is null-terminator.
size_t const filename_size = SFN_MAX + SFN_SUFFIX_LEN + 1;
TCHAR filename[filename_size];
get_filename(filename, filename_size);
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BYTE const mode = UART1_Read();

if (!SD_SPI_IsMediaPresent()) {
UART1_Write(FR_NOT_READY);
return DO_NOT_BOTHER;
}
FATFS drive;
DEBUG_write_u8(f_mount(&drive, "0:", 1));
DEBUG_write_u8(f_mount(&drive, SDCARD_DRIVE, 1));

FIL file;
// Host must wait for f_open before sending data.
Expand All @@ -41,38 +55,39 @@ response_t SDCARD_write_file(void) {
FSIZE_t data_size = UART1_read_u32();
FSIZE_t bytes_written = 0;

for (
FSIZE_t block_size, remaining = data_size;
block_size = remaining > BUF_MAX ? BUF_MAX : remaining,
remaining;
remaining -= block_size
) {
TCHAR buffer[block_size];
for (FSIZE_t block_size, remaining = data_size;
block_size = remaining > BUF_MAX ? BUF_MAX : remaining, remaining;
remaining -= block_size) {

for (UINT i = 0; i < block_size; ++i) {
buffer[i] = UART1_Read();
s_sector_buf[i] = UART1_Read();
}

WATCHDOG_TimerClear();
UINT written = 0;
// Host must wait for f_write before sending more data.
UART1_Write(f_write(&file, buffer, (UINT)block_size, &written));
UART1_Write(f_write(&file, s_sector_buf, (UINT)block_size, &written));
bytes_written += written;
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}

UART1_write_u32(bytes_written);
DEBUG_write_u8(f_close(&file));
DEBUG_write_u8(f_mount(0, "0:", 0));
DEBUG_write_u8(f_mount(0, SDCARD_DRIVE, 0));

return DO_NOT_BOTHER;
}

response_t SDCARD_read_file(void) {
response_t SDCARD_read_file(void)
{
TCHAR filename[SFN_MAX + SFN_SUFFIX_LEN + 1]; // +1 is null-terminator.
get_filename(filename, sizeof filename);

if (!SD_SPI_IsMediaPresent()) {
UART1_Write(FR_NOT_READY);
return DO_NOT_BOTHER;
}
FATFS drive;
DEBUG_write_u8(f_mount(&drive, "0:", 1));
DEBUG_write_u8(f_mount(&drive, SDCARD_DRIVE, 1));

FIL file;
DEBUG_write_u8(f_open(&file, filename, FA_READ));
Expand All @@ -82,36 +97,37 @@ response_t SDCARD_read_file(void) {
UART1_write_u32(info.fsize);
FSIZE_t bytes_read = 0;

for (
FSIZE_t block_size, remaining = info.fsize;
block_size = remaining > BUF_MAX ? BUF_MAX : remaining,
remaining;
remaining -= block_size
) {
for (FSIZE_t block_size, remaining = info.fsize;
block_size = remaining > BUF_MAX ? BUF_MAX : remaining, remaining;
remaining -= block_size) {
WATCHDOG_TimerClear();
UINT read = 0;
TCHAR buffer[block_size];
f_read(&file, &buffer, (UINT)block_size, &read);
f_read(&file, s_sector_buf, (UINT)block_size, &read);
bytes_read += read;

for (UINT i = 0; i < block_size; ++i) {
UART1_Write(buffer[i]);
UART1_Write(s_sector_buf[i]);
}
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}

UART1_write_u32(bytes_read);
DEBUG_write_u8(f_close(&file));
DEBUG_write_u8(f_mount(0, "0:", 0));
DEBUG_write_u8(f_mount(0, SDCARD_DRIVE, 0));

return DO_NOT_BOTHER;
}

response_t SDCARD_get_file_info(void) {
response_t SDCARD_get_file_info(void)
{
TCHAR filename[SFN_MAX + SFN_SUFFIX_LEN + 1]; // +1 is null-terminator.
get_filename(filename, sizeof filename);

if (!SD_SPI_IsMediaPresent()) {
UART1_Write(FR_NOT_READY);
return DO_NOT_BOTHER;
}
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FATFS drive;
DEBUG_write_u8(f_mount(&drive, "0:", 1));
DEBUG_write_u8(f_mount(&drive, SDCARD_DRIVE, 1));

FILINFO info = {0, 0, 0, 0, {0}};
DEBUG_write_u8(f_stat(filename, &info));
Expand All @@ -121,7 +137,7 @@ response_t SDCARD_get_file_info(void) {
UART1_WriteInt(info.ftime);
UART1_Write(info.fattrib);

DEBUG_write_u8(f_mount(0, "0:", 0));
DEBUG_write_u8(f_mount(0, SDCARD_DRIVE, 0));

return SUCCESS;
}
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