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

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Date:   Mon, 11 Jun 2018 17:28:16 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        "David S. 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,

>> 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.

Regards

Marcel