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    SubjectRe: [PATCH 1/2] remoteproc: maintain a generic child device for each rproc
    (Sorry your mail was lost due to mail outage)

    On 05/30/12 05:16, Ohad Ben-Cohen wrote:
    > On Wed, May 30, 2012 at 11:36 AM, Stephen Boyd <> wrote:
    >> One complaint I've gotten is that the error messages are essentially
    >> useless now. I believe there are some ongoing discussions on lkml to fix
    >> this by traversing the device hierarchy to find the "real" device but
    >> the hard part is finding the real device.
    > You probably refer to the discussions around the input subsystem's pull request.
    > I was thinking about that too when creating this patch, and it looks
    > like whatever Greg will come up with on that matter will benefit us
    > too. So taking that into account, it might make more sense to do stick
    > with the virtual device rather than use the real one here (we'll end
    > up having more information in the long run).

    Fair enough. Hopefully something comes out of that discussion since this
    will need it.

    >> I'm not clear on busses versus classes.
    > I think that busses is a whole lot more complex beast. Probably the
    > main indication we want one is when we need to match drivers to
    > devices.
    > In this case, I was more wondering between using a class to a device type.
    >> I recall seeing a thread where
    >> someone said classes were on the way out and shouldn't be used but I
    >> can't find it anymore.
    > I also remembered a similar discussion at a plumbers mini-conf about
    > 2-3 years ago too, so I looked at device_type as an alternative to
    > class. The former looks somewhat simpler, but I couldn't find any
    > major advantage for using one over the other, and both seem to be in
    > use by many subsystems.
    >> Should we use classes for devices that will never
    >> have a matching driver?
    > It's not strictly required, but in case we want to provide these
    > devices some common behavior (and in our case we want them all to have
    > the same release handler, and very soon, the same PM handlers, too),
    > then a class (or a type) is helpful.
    > It looks like moving from a class to a type is quite trivial, in case
    > classes do eventually go away (or an advantage of using the latter
    > shows up), but I'm not aware of any other viable alternative for us
    > other than class/type.

    Ok. Will moving from a class to a device type disrupt the kernel ABI?
    First it will be under /sys/class/ and then under /sys/bus? Greg, can
    you shed some light on when to use a class versus a device type?

    Sent by an employee of the Qualcomm Innovation Center, Inc.
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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