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>
---
v6:
        - remove device names array
        - check return value of dev_set_name()
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                         | 13 ++++++++++---
 tools/testing/selftests/vm/test_hmm.sh |  6 ------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index cfe632047839..7d1f98bc9c9a 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -86,7 +86,7 @@ struct dmirror_chunk {
  */
 struct dmirror_device {
 	struct cdev		cdevice;
-	struct hmm_devmem	*devmem;
+	struct device		device;
 
 	unsigned int		devmem_capacity;
 	unsigned int		devmem_count;
@@ -1227,7 +1227,14 @@ 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);
+	mdevice->device.devt = dev;
+
+	ret = dev_set_name(&mdevice->device, "hmm_dmirror%u", id);
+	if (ret)
+		return ret;
+
+	ret = cdev_device_add(&mdevice->cdevice, &mdevice->device);
 	if (ret)
 		return ret;
 
@@ -1254,7 +1261,7 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
 		kfree(mdevice->devmem_chunks);
 	}
 
-	cdev_del(&mdevice->cdevice);
+	cdev_device_del(&mdevice->cdevice, &mdevice->device);
 }
 
 static int __init hmm_dmirror_init(void)
diff --git a/tools/testing/selftests/vm/test_hmm.sh b/tools/testing/selftests/vm/test_hmm.sh
index 0647b525a625..69f5889f8575 100755
--- a/tools/testing/selftests/vm/test_hmm.sh
+++ b/tools/testing/selftests/vm/test_hmm.sh
@@ -41,17 +41,11 @@ check_test_requirements()
 load_driver()
 {
 	modprobe $DRIVER > /dev/null 2>&1
-	if [ $? == 0 ]; then
-		major=$(awk "\$2==\"HMM_DMIRROR\" {print \$1}" /proc/devices)
-		mknod /dev/hmm_dmirror0 c $major 0
-		mknod /dev/hmm_dmirror1 c $major 1
-	fi
 }
 
 unload_driver()
 {
 	modprobe -r $DRIVER > /dev/null 2>&1
-	rm -f /dev/hmm_dmirror?
 }
 
 run_smoke()
-- 
2.17.1

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

On Wed, Mar 30, 2022 at 03:47:25AM +0300, 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>
> ---
> v6:
>         - remove device names array
>         - check return value of dev_set_name()
> 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                         | 13 ++++++++++---
>  tools/testing/selftests/vm/test_hmm.sh |  6 ------
>  2 files changed, 10 insertions(+), 9 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason