From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH resend 1/4] scsi/sr: add no_read_disc_info scsi_device flag Date: Wed, 28 Jul 2010 08:19:55 -0500 Message-ID: <1280323195.30808.58.camel@mulgrave.site> References: <1279875174-2905-1-git-send-email-hdegoede@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1279875174-2905-1-git-send-email-hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Hans de Goede Cc: Tejun Heo , Alan Stern , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-scsi@vger.kernel.org On Fri, 2010-07-23 at 10:52 +0200, Hans de Goede wrote: > Some USB devices emulate a usb-mass-storage attached (scsi) cdrom device, > usually this fake cdrom contains the windows software for the device. > While working on supporting Appotech ax3003 based photoframes, which do > this I discovered that they will go of into lala land when ever they > see a READ_DISC_INFO scsi command. > > Thus this patch adds a scsi_device flag (which can then be set by the > usb-storage driver through an unsual-devs entry), to indicate this, and > makes the sr driver honor this flag. > > I know this sucks, but as discussed on linux-scsi list there is no other > way to make this device work properly. > > Looking at usb traces made under windows, windows never sends a > READ_DISC_INFO during normal interactions with a usb cdrom device. So as > this cdrom emulation thingie becomes more common we might see more of > this problem. So, I suppose we can do this. I dislike threading device bugs like this up and down the stack. The usb stor_control_thread already does some command filtering; if it just rejected this command and READ CAPACITY(16) on the flags, I think it would be far less code and the SCSI subsystem would just do the right thing. I'd actually like to hear from USB what they'd prefer to do. James -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html