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From: "Mika Penttilä" <mpenttil@redhat.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	apopple@nvidia.com, jhubbard@nvidia.com, rcampbell@nvidia.com,
	vbabka@suse.cz
Subject: Re: [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev
Date: Fri, 18 Mar 2022 04:34:20 +0200	[thread overview]
Message-ID: <10fb1261-f22f-8e21-4056-166c283e26f2@redhat.com> (raw)
In-Reply-To: <20220317141539.GD64706@ziepe.ca>



On 17.3.2022 16.15, Jason Gunthorpe wrote:
> On Thu, Mar 17, 2022 at 08:58:52AM +0200, Mika Penttilä wrote:
>> @@ -1225,7 +1232,11 @@ static int dmirror_device_init(struct dmirror_device
>> *mdevice, int id)
>>
>>          cdev_init(&mdevice->cdevice, &dmirror_fops);
>>          mdevice->cdevice.owner = THIS_MODULE;
>> -       ret = cdev_add(&mdevice->cdevice, dev, 1);
>> +       device_initialize(&mdevice->device);
>> +       dev_set_name(&mdevice->device, "%s", dmirror_device_names[id]);
>> +       mdevice->device.devt = dev;
>> +
>> +       ret = cdev_device_add(&mdevice->cdevice, &mdevice->device);
>>          if (ret)
>>                  return ret;
> 
> Right, miscdev isn't that helpful in the end..
> 
> Jason
> 

To wrap up, I could send a v3 formal patch with either this cdev way or 
the miscdev way.. Both eliminate the user space /proc/devices parsing 
and mknod'ing. Jason brought up concerns using miscdevice like this, 
although for this case it works correctly. miscdevice also provides a 
little more cleanup and simpler code, but the difference is not huge. So 
what do people prefer?

Thanks,
Mika


  reply	other threads:[~2022-03-18  2:34 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-11  3:30 [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev mpenttil
2022-03-11  6:15 ` John Hubbard
2022-03-11  6:18   ` Mika Penttilä
2022-03-14 18:24 ` Jason Gunthorpe
2022-03-15  3:22   ` Mika Penttilä
2022-03-15 18:39     ` Jason Gunthorpe
2022-03-17  5:47       ` Mika Penttilä
2022-03-17  6:58         ` Mika Penttilä
2022-03-17 14:15           ` Jason Gunthorpe
2022-03-18  2:34             ` Mika Penttilä [this message]
2022-03-18  2:58               ` John Hubbard
2022-03-18 12:40                 ` Jason Gunthorpe

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