Re: [PATCH 1/3] usb: gadget: storage: Add fsg_get_toc helper

[Roger Quadros]

Hi,

On 03/09/2011 06:07 PM, ext Alan Stern wrote:
> > +	case 2:
> > +		/* Raw TOC */
> > +		memset(buf, 0, 37);	/* Header + A0, A1&  A2 descriptors */
> > +		buf[1] = 37;		/* 4 + 3*11 */
>
> According to the SFF8020i spec Table 128, TOC Data Length is 2 + 11 *
> (number of descriptors returned).  But that's probably a misprint.

It's probably right. I will fix it and verify if it works.
> > +		buf[2] = 1;		/* First complete session */
> > +		buf[3] = 2;		/* Last complete session */
>
> According to the spec, for drives that do not support multi-session,
> the First session number should be equal to the Last session number.
Right. good catch.

> On Wed, 9 Mar 2011, Roger Quadros wrote:
>
> > Mac OS-X expects CD-ROM TOC in raw format (i.e. format:2). It also
> > sends the READ_TOC CDB in old style SFF8020i format. i.e. 2 format bits
> > are encoded in MSBs of CDB byte 9.
> >
> > This patch will enable CD-ROM emulation to work with Mac OS-X. Tested on
> > Mac OS X v10.6.3.
> >
> > Signed-off-by: Roger Quadros<roger.quadros@xxxxxxxxx>
> > ---
> >   drivers/usb/gadget/file_storage.c |   32 +++++++++++++++++++-------------
> >   1 files changed, 19 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
> > index a6eacb5..753ac94 100644
> > --- a/drivers/usb/gadget/file_storage.c
> > +++ b/drivers/usb/gadget/file_storage.c
> > @@ -1696,6 +1696,8 @@ static int do_read_toc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
> >   	int		msf = fsg->cmnd[1]&  0x02;
> >   	int		start_track = fsg->cmnd[6];
> >   	u8		*buf = (u8 *) bh->buf;
> > +	u8		format;
> > +	int		ret;
> >
> >   	if ((fsg->cmnd[1]&  ~0x02) != 0 ||		/* Mask away MSF */
> >   			start_track>  1) {
> > @@ -1703,18 +1705,22 @@ static int do_read_toc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
> >   		return -EINVAL;
> >   	}
> >
> > -	memset(buf, 0, 20);
> > -	buf[1] = (20-2);		/* TOC data length */
> > -	buf[2] = 1;			/* First track number */
> > -	buf[3] = 1;			/* Last track number */
> > -	buf[5] = 0x16;			/* Data track, copying allowed */
> > -	buf[6] = 0x01;			/* Only track is number 1 */
> > -	store_cdrom_address(&buf[8], msf, 0);
> > +	/*
> > +	 * Check if CDB is old style SFF-8020i
> > +	 * i.e. format is in 2 MSBs of byte 9
> > +	 * Mac OS-X host sends us this.
> > +	 */
> > +	format = (fsg->cmnd[9]>>  6)&  0x3;
> > +	if (format == 0)
> > +		format = fsg->cmnd[2]&  0xf;	/* new style MMC-2 */
>
> The spec says: "Format field definition: When Format in Byte 2 is zero,
> then Byte 9 is used."  This logic does not follow that description.

Yes indeed. I'll fix all this in v2. Thanks for review.

--
regards,
-roger
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