Re: [PATCH v2 08/10] gpio: aggregator: expoose aggregator created via legacy sysfs to configfs

[Koichiro Den <koichiro.den@xxxxxxxxxxxxx>]

On Tue, Feb 04, 2025 at 02:12:33PM GMT, Bartosz Golaszewski wrote:
> On Mon, Feb 3, 2025 at 4:12 AM Koichiro Den <koichiro.den@xxxxxxxxxxxxx> wrote:
> >
> > Expose settings for aggregators created using the sysfs 'new_device'
> > interface to configfs. Once written to 'new_device', an "_auto.<N>" path
> 
> I would prefer this to be called "_sysfs.<N>" as it's not really
> "automatic" - the user did create this, just with a different
> interface.

Makes sense, I'll change it in v3.

Thanks,
Koichiro

> 
> > appears in the configfs regardless of whether the probe succeeds.
> > Consequently, users can no longer use that prefix for custom GPIO
> > aggregator names. The 'live' attribute changes to 1 when the probe
> > succeeds and the GPIO forwarder is instantiated.
> >
> > Note that the aggregator device created via sysfs is asynchrnous, i.e.
> > writing into 'new_device' returns without waiting for probe completion,
> > and the probe may succeed, fail, or eventually succeed via deferred
> > probe. Thus, the 'live' attribute may change from 0 to 1 asynchronously
> > without notice. So, editting key/offset/name while it's waiting for
> > deferred probe is prohibited.
> >
> > The configfs auto-generation relies on create_default_group(), which
> > inherently prohibits rmdir(2). To align with the limitation, this commit
> > also prohibits mkdir(2) for them. When users want to change the number
> > of lines for an aggregator initialized via 'new_device', they need to
> > tear down the device using 'delete_device' and reconfigure it from
> > scratch. This does not break previous behaviour; users of legacy sysfs
> > interface simply gain additional almost read-only configfs exposure.
> >
> > Still, users can write into 'live' attribute to toggle the device unless
> > it's waiting for deferred probe. So once probe succeeds, they can
> > deactivate it in the same manner as the devices initialized via
> > configfs.
> >
> > Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxxxxxx>
> > ---
> 
> Bart