linux-kernel - Re: [PATCH RFC] mmc: add slot argument to mmc_of

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Date:	Wed, 14 May 2014 11:53:35 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Ludovic Desroches <ludovic.desroches@...el.com>
Cc:	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Chris Ball <chris@...ntf.net>
Subject: Re: [PATCH RFC] mmc: add slot argument to mmc_of_parse

On 7 May 2014 12:06, Ludovic Desroches <ludovic.desroches@...el.com> wrote:
> Some hosts manage several slots. In these case information such as the bus
> width, chip detect and others are into the slot node. So we have to parse
> child nodes. If not NULL, slot node will be used instead of the device
> node.
>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
> ---
>
> Hi,
>
> Since this patch is only a RFC, I have not yet updated drivers using this
> function.
>
> I would like to use mmc_of_parse to reduce code duplication. My issue is that
> atmel mci is a bit different from others mci host since it can provide
> several slots, so it allocates several mmc hosts. By the way, it is not the
> only one.
>
> When calling mmc_alloc_host, host->parent is set to &pdev->dev. mmc_of_parse
> uses host->parent->of_node but in my case settings are in the slot nodes so in
> the child nodes. That's why I would like to have a way to tell which node I
> want to use.

Seems reasonable, thanks for working on this!

>
>
> Regards
>
> Ludovic
>
>
>
>  drivers/mmc/core/host.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index fdea825..ed6cea5 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -300,13 +300,15 @@ static inline void mmc_host_clk_sysfs_init(struct mmc_host *host)
>  /**
>   *     mmc_of_parse() - parse host's device-tree node
>   *     @host: host whose node should be parsed.
> + *     @slot: some devices provide several slots so the node to parse
> + *     is not the host one.
>   *
>   * To keep the rest of the MMC subsystem unaware of whether DT has been
>   * used to to instantiate and configure this host instance or not, we
>   * parse the properties and set respective generic mmc-host flags and
>   * parameters.
>   */
> -int mmc_of_parse(struct mmc_host *host)
> +int mmc_of_parse(struct mmc_host *host, struct device_node *slot)
>  {
>         struct device_node *np;
>         u32 bus_width;
> @@ -317,7 +319,10 @@ int mmc_of_parse(struct mmc_host *host)
>         if (!host->parent || !host->parent->of_node)
>                 return 0;
>
> -       np = host->parent->of_node;
> +       if (slot)
> +               np = slot;
> +       else
> +               np = host->parent->of_node;
>
>         /* "bus-width" is translated to MMC_CAP_*_BIT_DATA flags */
>         if (of_property_read_u32(np, "bus-width", &bus_width) < 0) {
> --
> 1.7.9.5
>

How about adding a new API, __mmc_of_parse((struct mmc_host *host,
struct device_node *slot)
Then let the old API mmc_of_parse() remain as is, but let it call the
new API with slot == NULL.

Atmel can then use the new API, but the other drivers can remain as is.

Kind regards
Ulf Hansson
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