ALSA: scarlett2: Add ioctl commands to erase flash segments

Add ioctls:
- SCARLETT2_IOCTL_SELECT_FLASH_SEGMENT
- SCARLETT2_IOCTL_ERASE_FLASH_SEGMENT
- SCARLETT2_IOCTL_GET_ERASE_PROGRESS

The settings or the firmware flash segment can be selected and then
erased (asynchronous operation), and the erase progress can be
monitored.

If the erase progress is not monitored, then subsequent hwdep
operations will block until the erase is complete.

Once the erase is started, ALSA controls that communicate with the
device will all return -EBUSY, and the device must be rebooted.
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/227409adb672f174bf3db211e9bda016fb4646ea.1703001053.git.g@b4.vuSigned-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/sound/scarlett2.h

@@ -31,4 +31,24 @@
 /* Reboot */
 #define SCARLETT2_IOCTL_REBOOT _IO('S', 0x61)
 
+/* Select flash segment */
+#define SCARLETT2_SEGMENT_ID_SETTINGS 0
+#define SCARLETT2_SEGMENT_ID_FIRMWARE 1
+#define SCARLETT2_SEGMENT_ID_COUNT 2
+
+#define SCARLETT2_IOCTL_SELECT_FLASH_SEGMENT _IOW('S', 0x62, int)
+
+/* Erase selected flash segment */
+#define SCARLETT2_IOCTL_ERASE_FLASH_SEGMENT _IO('S', 0x63)
+
+/* Get selected flash segment erase progress
+ * 1 through to num_blocks, or 255 for complete
+ */
+struct scarlett2_flash_segment_erase_progress {
+	unsigned char progress;
+	unsigned char num_blocks;
+};
+#define SCARLETT2_IOCTL_GET_ERASE_PROGRESS \
+	_IOR('S', 0x64, struct scarlett2_flash_segment_erase_progress)
+
 #endif /* __UAPI_SOUND_SCARLETT2_H */