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    SubjectRe: [PATCH 5/6 v2] mtd: rawnand: ams-delta: use GPIO lookup table
    On Wed, 30 May 2018 22:39:03 +0200
    Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:

    > On Wednesday, May 30, 2018 7:52:20 PM CEST Boris Brezillon wrote:
    > > On Wed, 30 May 2018 19:43:09 +0200
    > >
    > > Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:
    > > > On Wednesday, May 30, 2018 11:05:00 AM CEST Boris Brezillon wrote:
    > > > > Hi Janusz,
    > > >
    > > > Hi Boris,
    > > >
    > > > > On Sat, 26 May 2018 00:20:45 +0200
    > > > >
    > > > > Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:
    > > > > > ...
    > > > > > Changes since v1:
    > > > > > - fix handling of devm_gpiod_get_optional() return values - thanks to
    > > > > >
    > > > > > Andy Shevchenko.
    > > > >
    > > > > Can you put the changelog after the "---" separator so that it does not
    > > > > appear in the final commit message?
    > > >
    > > > Yes, sure, sorry for that.
    > > >
    > > > > > +err_gpiod:
    > > > > > + if (err == -ENODEV || err == -ENOENT)
    > > > > > + err = -EPROBE_DEFER;
    > > > >
    > > > > Hm, isn't it better to make gpiod_find() return ERR_PTR(-EPROBE_DEFER)
    > > > > here [1]? At least, ENOENT should not be turned into EPROBE_DEFER,
    > > > > because it's returned when there's no entry matching the requested gpio
    > > > > in the lookup table, and deferring the probe won't solve this problem.
    > > >
    > > > ENOENT is also returned when no matching lookup table is found. That may
    > > > happen if consumer dev_name stored in the table differs from dev_name
    > > > assigned to the consumer by its bus, the platform bus in this case. For
    > > > that reason I think the consumer dev_name should be initialized in the
    > > > table after the device is registered, when its actual dev_name can be
    > > > obtained. If that device registration happens after the driver is already
    > > > registered, e.g., at late_initcall, the device is probed before its
    > > > lookup table is ready. For that reason returning EPROBE_DEFER seems
    > > > better to me even in the ENOENT case.
    > > Sorry, I don't get it. Aren't GPIO lookup tables supposed to be declared
    > > in board files, especially if the GPIO is used by a platform device?
    > > When would you have a lookup table registered later in the init/boot
    > > process?
    >
    > When e.g. I'd like to register my GPIO consumer platform device at
    > late_initcall for some reason, and I'm not sure what exact dev_name my
    > consomer will be registered with by the platform bus.

    You should know the name before the device is registered.

    > In that case I think I
    > should assign dev_name to the lookup table after the consumer device is
    > registered and its exact dev_name can be obtained, then register the table,

    I'm pretty sure it's not supposed to work like that. Resources attached
    to a device should be defined before the device is registered, not
    after, simply because when you call platform_device_register(), the
    device might be directly bind to the driver before the
    platform_device_register() calls return, and the driver will fail to
    probe the device if it doesn't find the GPIO it needs.

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