linux-kernel - Re: [RFC PATCHv2 4/5] hwmon: lis3: Remove the referencies to the global variable in core driver

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Date:	Thu, 7 Apr 2011 14:59:48 +0300 (EEST)
From:	Ilkka Koskinen <ikoskine@...ia.com>
To:	ext Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>
cc:	Ilkka Koskinen <ilkka.koskinen@...ia.com>,
	eric.piel@...mplin-utc.net, mjg@...hat.com,
	linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
	samu.p.onkalo@...ia.com
Subject: Re: [RFC PATCHv2 4/5] hwmon: lis3: Remove the referencies to the
 global variable in core driver


Hi,

Thanks for the comments!

On Tue, 5 Apr 2011, ext Thadeu Lima de Souza Cascardo wrote:
> On Tue, Apr 05, 2011 at 05:45:13PM +0300, Ilkka Koskinen wrote:
>> Signed-off-by: Ilkka Koskinen <ilkka.koskinen@...ia.com>
>> ---
>>  drivers/misc/lis3lv02d/lis3lv02d.c |  237 ++++++++++++++++++++----------------
>>  drivers/misc/lis3lv02d/lis3lv02d.h |    3 +
>>  2 files changed, 135 insertions(+), 105 deletions(-)

>> @@ -980,14 +1003,18 @@ int lis3lv02d_init_device(struct lis3lv02d *lis3)
>>  				thread_fn,
>>  				IRQF_TRIGGER_RISING | IRQF_ONESHOT |
>>  				irq_flags,
>> -				DRIVER_NAME, &lis3_dev);
>> +				DRIVER_NAME, lis3);
>>
>>  	if (err < 0) {
>>  		pr_err("Cannot get IRQ\n");
>>  		goto out;
>>  	}
>>
>> -	if (misc_register(&lis3lv02d_misc_device))
>> +	lis3->miscdev.minor	= MISC_DYNAMIC_MINOR;
>> +	lis3->miscdev.name	= "freefall";
>> +	lis3->miscdev.fops	= &lis3lv02d_misc_fops;
>> +
>> +	if (misc_register(&lis3->miscdev))
>>  		pr_err("misc_register failed\n");
>
> You should not use miscdevice in case there will be multiple devices.
> First, it will fail. There cannot be more than one device with the same
> name. Second, current dynamic minor devices is restricted to 64 devices.
> Since this is reserved to one-shot devices, freefall was OK as a misc
> device until you fixed it to allow multiple freefall devices.  :-)

Ah, true :)

> So, I'd recommend switching to a new device class, and have freefall0,
> freefall1, etc.

I wonder if introducing a new class makes sense. I mean, I can figure out 
use cases for several accelerometers but for several free fall sensors? :/

Would it be better to add a mechanism to tell to the core module if the 
particular device is used for free fall detection or not?

Cheers, Ilkka

> Anyway, good job on this.
>
> Regards,
> Cascardo.

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