linux-kernel - [PATCH v6] mm/hmm/test: use char dev with struct device to get device node

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Date:   Wed, 30 Mar 2022 03:47:25 +0300
From:   mpenttil@...hat.com
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     apopple@...dia.com, jhubbard@...dia.com, rcampbell@...dia.com,
        jgg@...pe.ca, vbabka@...e.cz,
        Mika Penttilä <mpenttil@...hat.com>
Subject: [PATCH v6] mm/hmm/test: use char dev with struct device to get device node

From: Mika Penttilä <mpenttil@...hat.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@...hat.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: Vlastimil Babka <vbabka@...e.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