diff options
| -rw-r--r-- | drivers/media/video/pvrusb2/pvrusb2-hdw.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/media/video/pvrusb2/pvrusb2-hdw.c b/drivers/media/video/pvrusb2/pvrusb2-hdw.c index 7fa903ad26bb..c8dedbab6e39 100644 --- a/drivers/media/video/pvrusb2/pvrusb2-hdw.c +++ b/drivers/media/video/pvrusb2/pvrusb2-hdw.c @@ -1313,6 +1313,17 @@ int pvr2_upload_firmware2(struct pvr2_hdw *hdw) if (bcnt > FIRMWARE_CHUNK_SIZE) bcnt = FIRMWARE_CHUNK_SIZE; memcpy(fw_ptr, fw_entry->data + fw_done, bcnt); /* Usbsnoop log shows that we must swap bytes... */ + /* Some background info: The data being swapped here is a + firmware image destined for the mpeg encoder chip that + lives at the other end of a USB endpoint. The encoder + chip always talks in 32 bit chunks and its storage is + organized into 32 bit words. However from the file + system to the encoder chip everything is purely a byte + stream. The firmware file's contents are always 32 bit + swapped from what the encoder expects. Thus the need + always exists to swap the bytes regardless of the endian + type of the host processor and therefore swab32() makes + the most sense. */ for (icnt = 0; icnt < bcnt/4 ; icnt++) ((u32 *)fw_ptr)[icnt] = swab32(((u32 *)fw_ptr)[icnt]); |