Re: [PATCH] i2c: mux: create proper topology in sysfs

Guenter Roeck
2014-11-03T20:55:34Z

On Sun, Nov 02, 2014 at 09:40:09PM +0100, Wolfram Sang wrote:
> The current implementation creates muxed i2c-<n> busses as immediate
> children of their i2c-<n> parent bus. In case of multiple muxes on one
> bus, it is impossible to determine which muxed bus comes from which mux.
>
> Change the topology so that they are created under the corresponding mux
> device. This way, multiple muxes on the same segment can coexist and
> children busses are grouped accordingly.
>
> So for instance, by adding a pca9547 device with address 0x70 to
> bus i2c-0, instead of:
>
> /sys/class/i2c-dev/i2c-0/device/i2c-1
> ...
> /sys/class/i2c-dev/i2c-0/device/i2c-8
>
> we get:
>
> /sys/class/i2c-dev/i2c-0/device/0-0070/i2c-1
> ...
> /sys/class/i2c-dev/i2c-0/device/0-0070/i2c-8
>
> Symlinks for backward compatibility are provided.
>
> Signed-off-by: Gerlando Falauto <gerlando.falauto-SkAbAL50j+5BDgjK7y7TUQ@public.gmane.org>
>
> [wsa: Ported to top-of-tree (1 line left :)) and added the compatibility
> links.]
> Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> Cc: Jean Delvare <jdelvare-l3A5Bk7waGM@public.gmane.org>
> Cc: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
> Cc: Martin Belanger <martin.belanger-Ir6+u9MVKBtBDgjK7y7TUQ@public.gmane.org>
> Cc: Rodolfo Giometti <giometti-AVVDYK/kqiJWk0Htik3J/w@public.gmane.org>
> Cc: Michael Lawnick <ml.lawnick-Mmb7MZpHnFY@public.gmane.org>
> Cc: Jeroen De Wachter <jeroen.de.wachter-CNXmb7IdZIWZIoH1IeqzKA@public.gmane.org>
> ---
>
> So, this is what I came up with to fix the mux-topology problem. Since I don't
> really use muxes, please review/comment/test. And give Acks/Tested-by tags if
> this works for you.
>
> drivers/i2c/i2c-mux.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
> index 2d0847b6be62..5b482ea32faf 100644
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -138,7 +138,7 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
> priv->adap.owner = THIS_MODULE;
> priv->adap.algo = &priv->algo;
> priv->adap.algo_data = priv;
> - priv->adap.dev.parent = &parent->dev;
> + priv->adap.dev.parent = mux_dev;
> priv->adap.retries = parent->retries;
> priv->adap.timeout = parent->timeout;
>
> @@ -183,6 +183,9 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
> return NULL;
> }
>
> + WARN(sysfs_create_link(&parent->dev.kobj, &priv->adap.dev.kobj, priv->adap.dev.kobj.name),
> + "can't create compatibility link for old mux name scheme\n");
> +
Something seems to be wrong with the linking.

I get lots of messages such as

sysfs: cannot create duplicate filename
'/devices/fff70a000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0/0000:02:09.0/0000:10:00.0/i2c-sam.16/i2c-88/i2c-89'

followed by "can't create compatibility link for old mux name scheme".

Guenter