adamksmith
a911b9e4cb
ESPHome external_component that presents a synthetic 64 KB FAT12 disk over the ESP32-S3's native USB-OTG, containing a one-byte switch_position file and a switch_position_grub.cfg snippet. The disk's volume serial is fixed at 0x55AA6922 to stay drop-in compatible with the upstream /etc/grub.d hook. Components: - fat12 / msc_disk: portable FAT12 sector synthesiser ported from reference/src/fat.c and the boot-sector / FAT / dir-entry generation in reference/src/usb.c. - usb_descriptors / tusb_glue: TinyUSB MSC class with our own callbacks delegating to MscDisk::read_lba (linker --allow-multiple-definition picks ours over esp_tinyusb's storage-backed defaults). - grub_boot_switch: top-level Component, NVS persistence on target changes, exposes targets table to sub-platforms. - select: HA-facing select platform reading parent's targets map. Validated end-to-end on an ESP32-S3-DevKitC-1: USB enumerates as 26ba:8003, /dev/sdb mounts FAT12, mtype reads back the live target, and POST /select/boot_target/set?option=Windows updates both files on the next host read.
81 lines
2.2 KiB
C++
81 lines
2.2 KiB
C++
#include "fat12.h"
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#include <string.h>
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namespace esphome {
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namespace grub_boot_switch {
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static inline uint8_t fat_checksum(const char *name) {
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uint8_t s = name[0];
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s = (s << 7) + (s >> 1) + name[1];
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s = (s << 7) + (s >> 1) + name[2];
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s = (s << 7) + (s >> 1) + name[3];
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s = (s << 7) + (s >> 1) + name[4];
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s = (s << 7) + (s >> 1) + name[5];
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s = (s << 7) + (s >> 1) + name[6];
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s = (s << 7) + (s >> 1) + name[7];
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s = (s << 7) + (s >> 1) + name[8];
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s = (s << 7) + (s >> 1) + name[9];
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s = (s << 7) + (s >> 1) + name[10];
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return s;
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}
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static uint8_t write_utf16_chars(const char *name, uint8_t *index, uint8_t length, uint8_t write_count,
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uint8_t *output) {
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for (uint8_t i = write_count; i != 0; --i) {
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if (*index <= length) {
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*output++ = name[*index];
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*output++ = 0x00;
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++(*index);
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} else {
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*output++ = 0xFF;
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*output++ = 0xFF;
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}
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}
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return write_count * 2;
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}
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uint8_t fat_write_lfn(const char *name, const FatDirEntry *direntry, uint8_t *output) {
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constexpr uint8_t kCharsPerEntry = 13;
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const size_t length = strlen(name);
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const uint8_t num_entries = (length + (kCharsPerEntry - 1)) / kCharsPerEntry;
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const uint8_t checksum = fat_checksum(reinterpret_cast<const char *>(direntry));
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for (uint8_t ordinal = num_entries; ordinal != 0; --ordinal) {
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uint8_t index = (ordinal - 1) * kCharsPerEntry;
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*output = ordinal | (kFat_LastLFN * (ordinal == num_entries));
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++output;
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output += write_utf16_chars(name, &index, length, 5, output);
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output[0] = kFatAttr_LongFileName;
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output[1] = 0x00;
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output[2] = checksum;
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output += 3;
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output += write_utf16_chars(name, &index, length, 6, output);
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output[0] = 0x00;
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output[1] = 0x00;
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output += 2;
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output += write_utf16_chars(name, &index, length, 2, output);
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}
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return sizeof(FatDirEntry) * num_entries;
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}
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uint8_t fat_write_dir(const FatDirEntry *direntry, uint8_t *output) {
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memcpy(output, direntry, sizeof(FatDirEntry));
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return sizeof(FatDirEntry);
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}
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uint16_t fat_date(uint16_t year, uint8_t month, uint8_t day) {
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return ((year - 1980) << 9) | (month << 5) | day;
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}
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} // namespace grub_boot_switch
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} // namespace esphome
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