New style i2c drivers for ALSA SoC

I am writing drivers to support ALSA SoC for an ARM based system. The system has an i2c codec. I want to use the new style driver for the codec driver, but I cannot get it to work properly. In my codec driver (sound/soc/codecs/tlv320aic2x.c) I have:

static struct i2c_driver aic2x_i2c_driver = {
	.driver		= {
		.name	= "tlv320aic2x",
		.owner	= THIS_MODULE,
	},
	.probe		= aic2x_i2c_probe,
	.remove		= aic2x_i2c_remove,
};

static int __init aic2x_init(void)

{
	return i2c_add_driver(&aic2x_i2c_driver);
}

static void __exit aic2x_exit(void)

{
	i2c_del_driver(&aic2x_i2c_driver);
}

module_init(aic2x_init);
module_exit(aic2x_exit);

Putting i2c_register_board_info either in my machine file in the arch/arm/ directory, or the machine file in the sound/soc/ directory does not seem to work. The driver does correctly register, ie I see the following in dmesg (although much later than the other i2c drivers):

i2c-core: driver [tlv320aic2x] registered

But its probe function is never called. The other i2c codec drivers in the sound/soc/codecs directory are all using the legacy i2c driver model.

I also looked at the i2c_new_device function. I'm not sure if this is what I want, but I don't know where to get the adapter structure to pass to it. The other drivers I found which use this function are creating their own i2c adapter (usually bit-bashed) for talking to the i2c device, which is not what I want to do.

Finally, a stylistic question: Should the i2c_board_info (or similar) for a codec device be defined in the machine initialisation code (arch/arm/ directory), or in the sound/soc machine file?

Hi Ryan,

Quoted 32 lines · Ryan Mallon

I am writing drivers to support ALSA SoC for an ARM based system. The system has an i2c codec. I want to use the new style driver for the codec driver, but I cannot get it to work properly. In my codec driver (sound/soc/codecs/tlv320aic2x.c) I have:

static struct i2c_driver aic2x_i2c_driver = {
	.driver		= {
		.name	= "tlv320aic2x",
		.owner	= THIS_MODULE,
	},
	.probe		= aic2x_i2c_probe,
	.remove		= aic2x_i2c_remove,
};

static int __init aic2x_init(void)

{
	return i2c_add_driver(&aic2x_i2c_driver);
}

static void __exit aic2x_exit(void)

{
	i2c_del_driver(&aic2x_i2c_driver);
}

module_init(aic2x_init);
module_exit(aic2x_exit);

Putting i2c_register_board_info either in my machine file in the arch/arm/ directory, or the machine file in the sound/soc/ directory does not seem to work. The driver does correctly register, ie I see the following in dmesg (although much later than the other i2c drivers):

Quoted 4 lines

i2c-core: driver [tlv320aic2x] registered

But its probe function is never called. The other i2c codec drivers in the sound/soc/codecs directory are all using the legacy i2c driver model.

What data are you passing to i2c_register_board_info?

Since 2.6.26-rc1, you can and should provide a list of devices supported by your driver. Your driver definition would look like:

static const struct i2c_device_id aic2x_i2c_id[] = {
	{ "tlv320aic2x", 0 },
	{ }
};

MODULE_DEVICE_TABLE(i2c, aic2x_i2c_id);

static struct i2c_driver aic2x_i2c_driver = {
	.driver		= {
		.name	= "tlv320aic2x",
		.owner	= THIS_MODULE,
	},
	.probe		= aic2x_i2c_probe,
	.remove		= aic2x_i2c_remove,
	.id_table	= aic2x_i2c_id,
};

Also note that there's already a driver in the kernel tree (drivers/media/video/tlv320aic23b.c) for apparently the same hardware, so maybe there's some code to share.

Quoted 5 lines

I also looked at the i2c_new_device function. I'm not sure if this is what I want, but I don't know where to get the adapter structure to pass to it. The other drivers I found which use this function are creating their own i2c adapter (usually bit-bashed) for talking to the i2c device, which is not what I want to do.

i2c_new_device() is meant to instantiate I2C devices at run-time. It is mostly useful for TV adapters and similar where you don't know in advance if it will be there and what i2c bus number it will receive. For embedded designs where you know exactly which devices you have at build time, i2c_register_board_info() is the way to go.

Quoted 3 lines

Finally, a stylistic question: Should the i2c_board_info (or similar) for a codec device be defined in the machine initialisation code (arch/arm/ directory), or in the sound/soc machine file?

Machine initialization code.

Quoted 3 lines · Jean Delvare

Since 2.6.26-rc1, you can and should provide a list of devices supported by your driver. Your driver definition would look like:

Quoted 5 lines

static const struct i2c_device_id aic2x_i2c_id[] = {
	{ "tlv320aic2x", 0 },
	{ }
};

MODULE_DEVICE_TABLE(i2c, aic2x_i2c_id);

Done. I had thought this was option if a driver only supported a single device?

Quoted 11 lines

static struct i2c_driver aic2x_i2c_driver = {
	.driver		= {
		.name	= "tlv320aic2x",
		.owner	= THIS_MODULE,
	},
	.probe		= aic2x_i2c_probe,
	.remove		= aic2x_i2c_remove,
	.id_table	= aic2x_i2c_id,
};

Quoted 3 lines

Also note that there's already a driver in the kernel tree (drivers/media/video/tlv320aic23b.c) for apparently the same hardware, so maybe there's some code to share.

Yes. The tlv320aic23b is both an audio codec and a video decoder of some sort. We only use the audio codec part on our particular board. The driver under drivers/media/video is pretty minimal, and appears that it may have been hard coded for a particular graphics card that it appears on? The driver I have for the audio codec is already substantially larger. There is also the problem that the soc codec stuff should live under sound/soc/codecs and video decoders should live under drivers/media/video. Assuming I post patches for my work at some stage (which I intend to do), perhaps it is easier to have two drivers to start with, and then merge them if people have hardware which is using both the audio and video codec functionality?

I am writing drivers to support ALSA SoC for an ARM based system. The system has an i2c codec. I want to use the new style driver for the codec driver, but I cannot get it to work properly. In my codec driver (sound/soc/codecs/tlv320aic2x.c) I have:

static struct i2c_driver aic2x_i2c_driver = {
	.driver		= {
		.name	= "tlv320aic2x",
		.owner	= THIS_MODULE,
	},
	.probe		= aic2x_i2c_probe,
	.remove		= aic2x_i2c_remove,
};

static int __init aic2x_init(void)

{
	return i2c_add_driver(&aic2x_i2c_driver);
}

static void __exit aic2x_exit(void)

{
	i2c_del_driver(&aic2x_i2c_driver);
}

module_init(aic2x_init);
module_exit(aic2x_exit);

Finally, a stylistic question: Should the i2c_board_info (or similar) for a codec device be defined in the machine initialisation code (arch/arm/ directory), or in the sound/soc machine file?