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SubjectRe: [PATCH v2] usb: gadget: f_mass_storage: Make CD-ROM emulation works with Windows OS
On Fri, Jun 24, 2022 at 10:19:16AM +0800, Neal Liu wrote:
> Add read TOC with format 1 to support CD-ROM emulation with
> Windows OS.
> This patch is tested on Windows OS Server 2019.
>
> Signed-off-by: Neal Liu <neal_liu@aspeedtech.com>
> ---
> drivers/usb/gadget/function/f_mass_storage.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
> index 3a77bca0ebe1..9edf76c22605 100644
> --- a/drivers/usb/gadget/function/f_mass_storage.c
> +++ b/drivers/usb/gadget/function/f_mass_storage.c
> @@ -1209,7 +1209,8 @@ static int do_read_toc(struct fsg_common *common, struct fsg_buffhd *bh)
>
> switch (format) {
> case 0:
> - /* Formatted TOC */
> + case 1:
> + /* Formatted TOC, Session info */

This comment is a little misleading. 0 is formatted TOC, and 1 is
multi-session info. The way you wrote it, it looks like the comment
applies to both formats. Do it like this:

case 0: /* Formatted TOC */
case 1: /* Multi-session info */

> len = 4 + 2*8; /* 4 byte header + 2 descriptors */
> memset(buf, 0, len);
> buf[1] = len - 2; /* TOC Length excludes length field */

It looks like you ignored one of the problems I pointed out in my
earlier email:

> When format is 1, the driver is supposed to ignore the start_track
> value. Your patch does not do this.

Please fix this.

Alan Stern

> @@ -1250,7 +1251,7 @@ static int do_read_toc(struct fsg_common *common, struct fsg_buffhd *bh)
> return len;
>
> default:
> - /* Multi-session, PMA, ATIP, CD-TEXT not supported/required */
> + /* PMA, ATIP, CD-TEXT not supported/required */
> curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
> return -EINVAL;
> }
> --
> 2.25.1
>

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