linux-kernel - Re: [PATCH v7 0/4] Extend device_get_match_data() to struct bus

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Date:   Tue, 15 Aug 2023 09:44:31 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Rosin <peda@...ntia.se>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Andi Shyti <andi.shyti@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v7 0/4] Extend device_get_match_data() to struct bus_type

On Fri, Aug 11, 2023 at 02:46:10PM +0000, Biju Das wrote:
> > Subject: Re: [PATCH v7 0/4] Extend device_get_match_data() to struct
> > bus_type
> > On Fri, Aug 11, 2023 at 01:27:36PM +0000, Biju Das wrote:
> > > > On Thu, Aug 10, 2023 at 09:05:10AM +0000, Biju Das wrote:

...

> > > > I'm good with this approach, but make sure you checked the whole
> > > > kernel source tree for a such.
> > >
> > > Checking against 16 is too short I guess??
> > >
> > > drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h has 18 enums.
> > 
> > So, what does prevent us from moving that tables to use pointers?
> 
> I think that will lead to ABI breakage(client->name vs id->name)
> 
> 	match = device_get_match_data(&client->dev);
> 	if (match) {
> 		chip_type = (uintptr_t)match;
> 		name = client->name;
> 	} else if (id) {
> 		chip_type = (enum inv_devices)
> 			id->driver_data;
> 		name = id->name;
> 	} else {
> 		return -ENOSYS;
> 	}


It's easy to work around (may be better fix can be found, haven't checked, just
what first comes to my mind):

	match ...
	name = match->name;

	/* If enumerated via firmware node, fix the ABI */
	if (dev_fwnode())
		client->name

> > > /*device enum */
> > > enum inv_devices {
> > > 	INV_MPU6050,
> > > 	INV_MPU6500,
> > > 	INV_MPU6515,
> > > 	INV_MPU6880,
> > > 	INV_MPU6000,
> > > 	INV_MPU9150,
> > > 	INV_MPU9250,
> > > 	INV_MPU9255,
> > > 	INV_ICM20608,
> > > 	INV_ICM20608D,
> > > 	INV_ICM20609,
> > > 	INV_ICM20689,
> > > 	INV_ICM20600,
> > > 	INV_ICM20602,
> > > 	INV_ICM20690,
> > > 	INV_IAM20680,
> > > 	INV_NUM_PARTS
> > > };
> > >
> > > The new helper function
> > 
> > You mean for debugging? We don't need that in production.
> 
> That is sample code for iterating through id table to find max enum
> and check against ZERO_OR_NULL_PTR

Much better with a coccinelle. You will find all or almost all occurrences
without too much effort done.

> > I think what you need is a coccinelle script to find these.
> 
> I need to explore using coccinelle script as I have n't tried before.

-- 
With Best Regards,
Andy Shevchenko