Re: [PATCH v2 resend] media: dvb: usb: Fix WARNING in dib0700_i2c_xfer/usb_submit_urb

Wolfram Sang
2025-03-29T06:05:53Z

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> 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.

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