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.
111 lines
3.8 KiB
C++
111 lines
3.8 KiB
C++
#include "usb_descriptors.h"
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#include <string.h>
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#include <stdio.h>
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#include "esp_mac.h"
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namespace esphome {
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namespace grub_boot_switch {
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// USB constants we need without dragging in <tusb.h> from this header
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constexpr uint8_t USB_DESC_DEVICE = 0x01;
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constexpr uint8_t USB_DESC_CONFIGURATION = 0x02;
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constexpr uint8_t USB_DESC_INTERFACE = 0x04;
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constexpr uint8_t USB_DESC_ENDPOINT = 0x05;
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constexpr uint8_t USB_CLASS_MSC = 0x08;
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constexpr uint8_t USB_MSC_SUBCLASS_SCSI = 0x06;
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constexpr uint8_t USB_MSC_PROTOCOL_BBB = 0x50;
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constexpr uint8_t EP_BULK = 0x02;
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// Mirrors the layout in reference/src/usb.c so the host sees the same shape
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// as the original STM32 firmware.
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constexpr uint8_t MSC_EP_IN = 0x81;
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constexpr uint8_t MSC_EP_OUT = 0x01;
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constexpr uint16_t MSC_EP_SIZE = 64; // Full-speed bulk
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static void put16le(uint8_t *p, uint16_t v) {
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p[0] = v & 0xFF;
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p[1] = (v >> 8) & 0xFF;
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}
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void usb_descriptors_build(UsbDescriptorBundle *b, uint16_t vid, uint16_t pid,
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const char *manufacturer, const char *product,
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const char *serial_override) {
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// ---- Device descriptor ----
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uint8_t *d = b->device;
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d[0] = 18; // bLength
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d[1] = USB_DESC_DEVICE; // bDescriptorType
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put16le(d + 2, 0x0200); // bcdUSB
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d[4] = 0x00; // bDeviceClass (defined in interface)
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d[5] = 0x00; // bDeviceSubClass
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d[6] = 0x00; // bDeviceProtocol
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d[7] = 64; // bMaxPacketSize0
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put16le(d + 8, vid);
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put16le(d + 10, pid);
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put16le(d + 12, 0x0200); // bcdDevice
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d[14] = 1; // iManufacturer (string index)
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d[15] = 2; // iProduct
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d[16] = 3; // iSerialNumber
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d[17] = 1; // bNumConfigurations
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// ---- Configuration descriptor (config + interface + 2 endpoints) ----
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uint8_t *c = b->config;
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// Configuration
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c[0] = 9;
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c[1] = USB_DESC_CONFIGURATION;
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put16le(c + 2, 32); // wTotalLength
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c[4] = 1; // bNumInterfaces
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c[5] = 1; // bConfigurationValue
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c[6] = 0; // iConfiguration
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c[7] = 0x80; // bmAttributes (bus powered)
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c[8] = 50; // bMaxPower (100mA)
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// Interface
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c[9] = 9;
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c[10] = USB_DESC_INTERFACE;
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c[11] = 0; // bInterfaceNumber
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c[12] = 0; // bAlternateSetting
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c[13] = 2; // bNumEndpoints
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c[14] = USB_CLASS_MSC;
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c[15] = USB_MSC_SUBCLASS_SCSI;
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c[16] = USB_MSC_PROTOCOL_BBB;
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c[17] = 0; // iInterface
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// Endpoint OUT
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c[18] = 7;
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c[19] = USB_DESC_ENDPOINT;
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c[20] = MSC_EP_OUT;
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c[21] = EP_BULK;
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put16le(c + 22, MSC_EP_SIZE);
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c[24] = 0;
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// Endpoint IN
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c[25] = 7;
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c[26] = USB_DESC_ENDPOINT;
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c[27] = MSC_EP_IN;
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c[28] = EP_BULK;
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put16le(c + 29, MSC_EP_SIZE);
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c[31] = 0;
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// ---- Strings ----
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// Index 0: language ID (English, US) — esp_tinyusb expects index 0 to be the
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// language; it builds the actual descriptor from a static "0x0409" string.
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static const char kLang[] = {0x09, 0x04, 0};
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b->strings[0] = kLang;
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b->strings[1] = manufacturer;
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b->strings[2] = product;
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if (serial_override && serial_override[0] != '\0') {
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snprintf(b->serial_buf, sizeof(b->serial_buf), "%s", serial_override);
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} else {
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uint8_t mac[6] = {};
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esp_read_mac(mac, ESP_MAC_WIFI_STA);
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snprintf(b->serial_buf, sizeof(b->serial_buf), "%02X%02X%02X%02X%02X%02X", mac[0],
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mac[1], mac[2], mac[3], mac[4], mac[5]);
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}
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b->strings[3] = b->serial_buf;
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}
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} // namespace grub_boot_switch
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} // namespace esphome
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