linux-kernel - Re: [PATCH v2 15/24] net: qualcomm: MODULE_DEVICE

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Message-ID: <CAPybu_2ViGvN6egz-Ajq4+1fv6VAVFswuvSPAVmYH0a9R-Yjvw@mail.gmail.com>
Date:   Mon, 11 Jun 2018 17:33:53 +0200
From:   Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        David Miller <davem@...emloft.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Rob Herring <robh@...nel.org>, Johan Hovold <johan@...nel.org>,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 15/24] net: qualcomm: MODULE_DEVICE_TABLE(serdev)

Hi Marcel,
On Mon, Jun 11, 2018 at 5:28 PM Marcel Holtmann <marcel@...tmann.org> wrote:
>
> Hi Marcel,
>
> >> the commit message is misleading me. If I build something with ACPI or DT support, then modinfo will show all modalias information for ACPI and DT compatible strings. What else does udev/modprobe actually need? Is something broken with the modalias export?
> >
> > The main purpose is to autoload drivers for devices that have been
> > created via sysfs or another module.
> >
> > Eg1: We have a serial port on a standard computer that has connected a
> > GPS module. Since it is something that is not in the ACPI nor the DT
> > table the user will run
> >
> > echo serdev_gps > /sys/bus/serial/devices/serial0/new_device
> >
> > Eg2 module: https://github.com/ribalda/linux/blob/415bb3f0076c2b846ebe5409589b8e1e3004f55a/drivers/tty/serdev/test_platform.c
> >
> > Modprobe does not know what module to load for that device unless
> > there is a matching MODULE_DEVICE_TABLE
> > Today, we have the same functionality for i2c devices
> > https://www.kernel.org/doc/Documentation/i2c/instantiating-devices
>
> but why does this have to be the driver name? I would rather say, create a generic string that describes the hardware and then use that. I think you also want the special handling, as from USB for example, that lets you reference an existing .compatible or ACPI ID as reference so that the driver_data is copied.

We can choose any name, but if there are no special variants (like the
rave-sp driver) I would prefer using the module name. We can of course
use more names, like the part number of the the device, but it is very
convenient to also use the module name, and other subsystems also do
that.

If you want to add specific names for this device please let me know
and I will add them to the list. You know much more about this module
than myself.

Thanks!

>
> Regards
>
> Marcel
>


-- 
Ricardo Ribalda