linux-kernel - Re: DVB: af9015 defunct [was: mmotm 2010-10-20-15-01 uploaded]

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Message-ID: <4CC85633.6030707@iki.fi>
Date:	Wed, 27 Oct 2010 19:41:23 +0300
From:	Antti Palosaari <crope@....fi>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>
CC:	Jiri Slaby <jirislaby@...il.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, mm-commits@...r.kernel.org,
	Greg KH <gregkh@...e.de>, USB list <linux-usb@...r.kernel.org>
Subject: Re: DVB: af9015 defunct [was: mmotm 2010-10-20-15-01 uploaded]

On 10/27/2010 07:12 PM, Mauro Carvalho Chehab wrote:
> int tda18271_write_regs(struct dvb_frontend *fe, int idx, int len)
> {
> ...
>          switch (priv->small_i2c) {
>          case TDA18271_03_BYTE_CHUNK_INIT:
>                  max = 3;
>                  break;
>          case TDA18271_08_BYTE_CHUNK_INIT:
>                  max = 8;
>                  break;
>          case TDA18271_16_BYTE_CHUNK_INIT:
>                  max = 16;
>                  break;
>          case TDA18271_39_BYTE_CHUNK_INIT:
>          default:
>                  max = 39;
>          }
>
>
> with small_i2c = 1, the driver will not restrict the maximum length size.
>
> It's weird that the patch didn't fix it. Are you sure that reverting this
> patch is enough to make the driver work?
>
> Please test this one.
>
> It will properly log the size of the message the driver tried to use, and will
> reduce the max number of bytes per I2C transfer to 8.

All in all, this small_i2c was added (Michael Krufky and I) when this 
tuner was taken in use with af9015 and it was 16 bytes initially. I 
think those other chunks are added later.
AF9015 I2C adapter can write 21 bytes at once.
Correct solution is to add option which splits writes as wanted (like 
option .i2c_wr_max) to the TDA18271. I have no HW to test.

Antti
-- 
http://palosaari.fi/
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