linux-kernel - Re: [PATCH 1/3] iio: adc: at91_adc: Repair broken platform

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Message-ID: <5318C950.7060900@kernel.org>
Date:	Thu, 06 Mar 2014 19:15:28 +0000
From:	Jonathan Cameron <jic23@...nel.org>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>
CC:	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Josh Wu <josh.wu@...el.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org
Subject: Re: [PATCH 1/3] iio: adc: at91_adc: Repair broken platform_data support

On 05/03/14 16:57, Alexandre Belloni wrote:
> Trying to use the at91_adc driver while not using device tree is ending up in a
> kernel crash:
>
> Unable to handle kernel NULL pointer dereference at virtual address 00000004
> [...]
> [<c01f3510>] (at91_adc_probe) from [<c0183828>] (platform_drv_probe+0x18/0x48)
> [<c0183828>] (platform_drv_probe) from [<c01824a4>] (driver_probe_device+0x100/0x218)
> [<c01824a4>] (driver_probe_device) from [<c0182648>] (__driver_attach+0x8c/0x90)
> [<c0182648>] (__driver_attach) from [<c0180de4>] (bus_for_each_dev+0x58/0x88)
> [<c0180de4>] (bus_for_each_dev) from [<c0181c7c>] (bus_add_driver+0xd4/0x1d4)
> [<c0181c7c>] (bus_add_driver) from [<c0182c40>] (driver_register+0x78/0xf4)
> [<c0182c40>] (driver_register) from [<c0008998>] (do_one_initcall+0xe8/0x14c)
> [<c0008998>] (do_one_initcall) from [<c02f0b50>] (kernel_init_freeable+0xec/0x1b4)
> [<c02f0b50>] (kernel_init_freeable) from [<c022acdc>] (kernel_init+0x8/0xe4)
> [<c022acdc>] (kernel_init) from [<c0009670>] (ret_from_fork+0x14/0x24)
>
> This is because the at91_adc_caps structure is mandatory but is not filled when
> using platform_data. Correct that by using an id_table. It ensues that the
> driver will not match "at91_adc" anymore but it was crashing anyway.
>
> Fixes: c46016665fff (iio: at91: ADC start-up time calculation changed since at91sam9x5)
> Cc: stable@...r.kernel.org # v3.13+
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Ouch.

It's late in the cycle so I'll send this on to Greg KH with a note
to say either send it to Linus if he is happy doing so - or send
it early in 3.15, then it'll get picked up for stable.

I'll give it a day or so to see if I the at91 maintainers are happy
with the other two parts as it is probably cleaner if all 3 go together.

Applied to the fixes-togreg branch of iio.git

Thanks,

Jonathan


> ---
>   drivers/iio/adc/at91_adc.c | 26 ++++++++++++++++++++++----
>   1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
> index 5b1aa027c034..bbba014c9939 100644
> --- a/drivers/iio/adc/at91_adc.c
> +++ b/drivers/iio/adc/at91_adc.c
> @@ -765,14 +765,17 @@ static int at91_adc_probe_pdata(struct at91_adc_state *st,
>   	if (!pdata)
>   		return -EINVAL;
>
> +	st->caps = (struct at91_adc_caps *)
> +			platform_get_device_id(pdev)->driver_data;
> +
>   	st->use_external = pdata->use_external_triggers;
>   	st->vref_mv = pdata->vref;
>   	st->channels_mask = pdata->channels_used;
> -	st->num_channels = pdata->num_channels;
> +	st->num_channels = st->caps->num_channels;
>   	st->startup_time = pdata->startup_time;
>   	st->trigger_number = pdata->trigger_number;
>   	st->trigger_list = pdata->trigger_list;
> -	st->registers = pdata->registers;
> +	st->registers = &st->caps->registers;
>
>   	return 0;
>   }
> @@ -1101,7 +1104,6 @@ static int at91_adc_remove(struct platform_device *pdev)
>   	return 0;
>   }
>
> -#ifdef CONFIG_OF
>   static struct at91_adc_caps at91sam9260_caps = {
>   	.calc_startup_ticks = calc_startup_ticks_9260,
>   	.num_channels = 4,
> @@ -1154,11 +1156,27 @@ static const struct of_device_id at91_adc_dt_ids[] = {
>   	{},
>   };
>   MODULE_DEVICE_TABLE(of, at91_adc_dt_ids);
> -#endif
> +
> +static const struct platform_device_id at91_adc_ids[] = {
> +	{
> +		.name = "at91sam9260-adc",
> +		.driver_data = (unsigned long)&at91sam9260_caps,
> +	}, {
> +		.name = "at91sam9g45-adc",
> +		.driver_data = (unsigned long)&at91sam9g45_caps,
> +	}, {
> +		.name = "at91sam9x5-adc",
> +		.driver_data = (unsigned long)&at91sam9x5_caps,
> +	}, {
> +		/* terminator */
> +	}
> +};
> +MODULE_DEVICE_TABLE(platform, at91_adc_ids);
>
>   static struct platform_driver at91_adc_driver = {
>   	.probe = at91_adc_probe,
>   	.remove = at91_adc_remove,
> +	.id_table = at91_adc_ids,
>   	.driver = {
>   		   .name = DRIVER_NAME,
>   		   .of_match_table = of_match_ptr(at91_adc_dt_ids),
>

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