Re: [RFC 1/2] mmc: read mmc alias from device tree

From: Doug Anderson
Date: Fri Mar 13 2015 - 16:09:27 EST


Hi,

On Tue, Apr 1, 2014 at 1:35 PM, <stefan@xxxxxxxx> wrote:
> From: Stefan Agner <stefan@xxxxxxxx>
>
> To get the SD/MMC host device ID, read the alias from the device
> tree.
>
> This is useful in case a SoC has multipe SD/MMC host controllers while
> the second controller should logically be the first device (e.g. if
> the second controller is connected to an internal eMMC). Combined
> with block device numbering using MMC/SD host device ID, this
> results in predictable name assignment of the internal eMMC block
> device.
>
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
> ---
> drivers/mmc/core/host.c | 24 +++++++++++++++++++-----
> 1 file changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 49bc403..29f44cf 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -448,8 +448,8 @@ EXPORT_SYMBOL(mmc_of_parse);
> */
> struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
> {
> - int err;
> struct mmc_host *host;
> + int of_id = -1, id = -1;
>
> host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
> if (!host)
> @@ -459,12 +459,26 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
> host->rescan_disable = 1;
> idr_preload(GFP_KERNEL);
> spin_lock(&mmc_host_lock);
> - err = idr_alloc(&mmc_host_idr, host, 0, 0, GFP_NOWAIT);
> - if (err >= 0)
> - host->index = err;
> +
> + if (dev->of_node)
> + of_id = of_alias_get_id(dev->of_node, "mmc");

Not that there's much chance of such an old patch landing, but just in
case anyone finds this Dmitry points out that this causes a
"scheduling while atomic". A fix is to move the "of_alias_get_id" up
above the spin_lock():

https://chromium-review.googlesource.com/#/c/259916/

-Doug
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