Re: [PATCH 08/12] backports: disable DVB_RTL2832 and DVB_USB_RTL28XXU

[Mauro Carvalho Chehab <m.chehab@samsung.com>]

Em Mon, 07 Apr 2014 20:32:19 -0700
"Luis R. Rodriguez" <mcgrof@do-not-panic.com> escreveu:

> Commit bcf43393 as of linux-next next-20140320 added this Makefile
> header extension:
> 
> ccflags-y += -I$(srctree)/drivers/staging/media/rtl2832u_sdr
> 
> This ends up calling a staging exported symbol rtl2832_sdr_attach().
> Let's not pollute driver code with staging code or dependencies.
> 
> Folks, can this be cleaned up? This sets a precedent for doing more
> of this, and this can get hairy. Its also not fair for folks who
> don't want to carry over any staging code. This forces them to, and
> its not just a header file, its a full exported symbol. What about
> synchronization with differen trees? Was this addressed with Greg?

The SDR code is at staging not because it has low quality, but because
we're still testing the SDR API before setting it into a stone.

The rtl2832u can operate in two modes: DVB-T and SDR. On DVB-T,
the hardware collects samples of a tuned channel and decodes it
with a hardware decoder, sending to userspace a MPEG TS stream.

On SDR, the hardware decoder is disabled, and the raw samples
are sent to userspace.

Yet, I agree that, if the SDR code is disabled, the rtl2832_sdr_attach()
should not be called. However, the code seems to be doing it
already. Take a look at drivers/staging/media/rtl2832u_sdr/rtl2832_sdr.h:

#if IS_ENABLED(CONFIG_DVB_RTL2832_SDR)
extern struct dvb_frontend *rtl2832_sdr_attach(struct dvb_frontend *fe,
	struct i2c_adapter *i2c, const struct rtl2832_config *cfg,
	struct v4l2_subdev *sd);
#else
static inline struct dvb_frontend *rtl2832_sdr_attach(struct dvb_frontend *fe,
	struct i2c_adapter *i2c, const struct rtl2832_config *cfg,
	struct v4l2_subdev *sd)
{
	dev_warn(&i2c->dev, "%s: driver disabled by Kconfig\n", __func__);
	return NULL;
}
#endif

Antti, please correct if I'm wrong, but the rtl2832u_tuner_attach()
code seems to not expect that the attach code succeeds. So, the only thing
that will happen DVB_RTL2832_SDR is disabled is that warning saying that
SDR is disabled will be sent to dmesg.

So, I don't see why to disable the entire driver due to that. Instead,
Just revert changeset bcf43393579e at the backport trees should be enough,
if don't want to backport the SDR driver.

Regards,
Mauro

> commit bcf43393579e3d4069e75a9200a87703185bcf11
> Author: Antti Palosaari <crope@iki.fi>
> Date:   Tue Sep 10 00:13:57 2013 -0300
> 
>     [media] rtl28xxu: attach SDR extension module
> 
>     With that extension module it supports SDR.
> 
>     Signed-off-by: Antti Palosaari <crope@iki.fi>
>     Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
> 
> Cc: Antti Palosaari <crope@iki.fi>
> Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
> ---
>  dependencies | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/dependencies b/dependencies
> index 6193ed1..b85268d 100644
> --- a/dependencies
> +++ b/dependencies
> @@ -185,8 +185,13 @@ VIDEO_RENESAS_VSP1 3.6
>  # This was added as of 3.7. Although we should be able to only enable
>  # this for 3.7 DVB_USB_RTL28XXU ends up selecting DVB_RTL2832 and
>  # that seems to currently require pegging both.
> -DVB_RTL2832 3.7
> -DVB_USB_RTL28XXU 3.7
> +#
> +# DVB_USB_RTL28XXU has a nasty ccflag usage thoug that includes staging
> +# headers introduced via commit bcf43393:
> +# ccflags-y += -I$(srctree)/drivers/staging/media/rtl2832u_sdr
> +# Let's not support this nastiness.
> +DVB_RTL2832 DISABLE
> +DVB_USB_RTL28XXU DISABLE
>  
>  # struct gpio_chip only got the required members in 2.6.28
>  BCMA_DRIVER_GPIO 2.6.28


-- 

Regards,
Mauro