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Sat, 29 Mar 2025 07:31:56 -0700 (PDT) Date: Sat, 29 Mar 2025 10:31:52 -0400 From: Alan Stern To: Wolfram Sang , Mauro Carvalho Chehab , syzbot , gregkh@linuxfoundation.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH v2 resend] media: dvb: usb: Fix WARNING in dib0700_i2c_xfer/usb_submit_urb Message-ID: References: <24798648-c5a3-4e31-9897-4610053007f3@rowland.harvard.edu> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Sat, Mar 29, 2025 at 07:05:49AM +0100, Wolfram Sang wrote: > > > In the case of dib0700, it was clear from the source code that the > > driver uses USB Control transfers to tell the hardware about I2C > > messages. I don't know if other bridges work in the same way. In > > theory a bridge could use USB Bulk transfers instead; they aren't > > subject to this restriction on length-0 reads. Or a bridge could use a > > Control read transfer but include extra header material along with the > > actual data, so that a length-0 message wouldn't end up generating a > > length-0 read. > > Fully understood, thanks for your explanation. > > > So the short answer is that you would need to find someone who really > > understands what's going on here -- which I don't. Sorry. > > No worries. There are only 5 drivers or so, I will manually check if > they use a control_read and have no own header. Doesn't sound hard. Good... Feel free to ask me if you have any questions or need any other help. Alan Stern