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SubjectRe: [PATCH v5] mm/hmm/test: use char dev with struct device to get device node
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On 25.3.2022 20.17, Jason Gunthorpe wrote:
> On Tue, Mar 22, 2022 at 06:35:43AM +0200, mpenttil@redhat.com wrote:
>> From: Mika Penttilä <mpenttil@redhat.com>
>>
>> HMM selftests use an in-kernel pseudo device to emulate device private
>> memory. The pseudo device registers a major device range for two pseudo
>> device instances. User space has a script that reads /proc/devices in
>> order to find the assigned major number, and sends that to mknod(1),
>> once for each node.
>>
>> Change this to properly use cdev and struct device APIs.
>>
>> Delete the /proc/devices parsing from the user-space test script, now
>> that it is unnecessary.
>>
>> Also, deleted an unused field in struct dmirror_device: devmem.
>>
>> Signed-off-by: Mika Penttilä <mpenttil@redhat.com>
>> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>> Cc: Alistair Popple <apopple@nvidia.com>
>> Cc: Ralph Campbell <rcampbell@nvidia.com>
>> Cc: Jason Gunthorpe <jgg@ziepe.ca>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> v5:
>> - fix whitespace
>> . delete unused structure field
>> v4:
>> - fix commit log
>> v3:
>> - use cdev_device_add() instead of miscdevice
>> v2:
>> - Cleanups per review comments from John Hubbard
>> - Added Tested-by and Ccs
>>
>> lib/test_hmm.c | 18 ++++++++++++++----
>> tools/testing/selftests/vm/test_hmm.sh | 6 ------
>> 2 files changed, 14 insertions(+), 10 deletions(-)
>>
>> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
>> index 767538089a62..3c7f2a92b09e 100644
>> +++ b/lib/test_hmm.c
>> @@ -29,11 +29,17 @@
>>
>> #include "test_hmm_uapi.h"
>>
>> -#define DMIRROR_NDEVICES 2
>> #define DMIRROR_RANGE_FAULT_TIMEOUT 1000
>> #define DEVMEM_CHUNK_SIZE (256 * 1024 * 1024U)
>> #define DEVMEM_CHUNKS_RESERVE 16
>>
>> +static const char *dmirror_device_names[] = {
>> + "hmm_dmirror0",
>> + "hmm_dmirror1"
>> +};
>> +
>> +#define DMIRROR_NDEVICES ARRAY_SIZE(dmirror_device_names)
>> +
>> static const struct dev_pagemap_ops dmirror_devmem_ops;
>> static const struct mmu_interval_notifier_ops dmirror_min_ops;
>> static dev_t dmirror_dev;
>> @@ -83,7 +89,7 @@ struct dmirror_chunk {
>> */
>> struct dmirror_device {
>> struct cdev cdevice;
>> - struct hmm_devmem *devmem;
>> + struct device device;
>>
>> unsigned int devmem_capacity;
>> unsigned int devmem_count;
>> @@ -1225,7 +1231,11 @@ 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]);
>
> Just
> dev_set_name(&mdevice->device, "hmm_dmirror%u", id);
>
> No need for an array

Yeah, no absolute need, thought names in an array is less hardcoded wrt
device node count and naming standard.

>
> Also check for error

True. Interesting fact is that even the device core itself doesn't check
for errors calling dev_set_name(), but sure it can fail in memory
allocations.

>
> Jason
>

Mika

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