linux-kernel - Re: [PATCH v2 6/6] of_spi: Initialize cs_gpios and cs

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Date:	Mon, 11 Feb 2013 00:23:20 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Andreas Larsson <andreas@...sler.com>
Cc:	Rob Herring <rob.herring@...xeda.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	devicetree-discuss@...ts.ozlabs.org,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, software@...sler.com
Subject: Re: [PATCH v2 6/6] of_spi: Initialize cs_gpios and cs_gpio with -EEXIST

On Tue, 29 Jan 2013 15:53:43 +0100, Andreas Larsson <andreas@...sler.com> wrote:
> Holes in the cs-gpios DT phandle list is supposed to mark that native
> chipselects is to be used. The value returned from of_get_named_gpio_flags in
> this case is -EEXIST. By initializing cs_gpios and cs_gpio with -EEXIST, this
> and only this errno will indicate to a spi controller driver that a native
> chipselect is to be used.
> 
> Signed-off-by: Andreas Larsson <andreas@...sler.com>

I've left this one off for now. Take a look at the patch I posted and
let me know if you think this one should still be applied.

g.

> ---
>  drivers/spi/spi.c       |    4 ++--
>  include/linux/spi/spi.h |    7 +++++--
>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 6f1b717..7494bad 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -334,7 +334,7 @@ struct spi_device *spi_alloc_device(struct spi_master *master)
>  	spi->dev.parent = &master->dev;
>  	spi->dev.bus = &spi_bus_type;
>  	spi->dev.release = spidev_release;
> -	spi->cs_gpio = -EINVAL;
> +	spi->cs_gpio = -EEXIST;
>  	device_initialize(&spi->dev);
>  	return spi;
>  }
> @@ -1097,7 +1097,7 @@ static int of_spi_register_master(struct spi_master *master)
>  	}
>  
>  	for (i = 0; i < master->num_chipselect; i++)
> -		cs[i] = -EINVAL;
> +		cs[i] = -EEXIST;
>  
>  	for (i = 0; i < nb; i++)
>  		cs[i] = of_get_named_gpio_flags(np, "cs-gpios", i, &flags[i]);
> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
> index 96b1055..0701882 100644
> --- a/include/linux/spi/spi.h
> +++ b/include/linux/spi/spi.h
> @@ -58,7 +58,8 @@ extern struct bus_type spi_bus_type;
>   * @modalias: Name of the driver to use with this device, or an alias
>   *	for that name.  This appears in the sysfs "modalias" attribute
>   *	for driver coldplugging, and in uevents used for hotplugging
> - * @cs_gpio: Negative or gpio for chip select.
> + * @cs_gpio: Negative or gpio for chip select.  Set to -EEXIST when chipselect
> + *	should be handled natively by the controller driver
>   * @cs_gpio_flags: of_gpio_flags corresponding to cs_gpio
>   *
>   * A @spi_device is used to interchange data between an SPI slave
> @@ -262,7 +263,9 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
>   * @unprepare_transfer_hardware: there are currently no more messages on the
>   *	queue so the subsystem notifies the driver that it may relax the
>   *	hardware by issuing this call
> - * @cs_gpios: possible array of negative values or gpios for chip selects
> + * @cs_gpios: possible array of negative values or gpios for chip selects.  A
> + *	chipselect that should be handled natively by the controller driver is
> + *	set to -EEXIST.
>   * @cs_gpio_flags: possible array of of_gpio_flags corresponding to cs_gpios
>   *
>   * Each SPI master controller can communicate with one or more @spi_device
> -- 
> 1.7.0.4
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
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