linux-kernel - [PATCH v5] mm/hmm/test: use char dev with struct device to get device node

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Message-Id: <20220322043543.18424-1-mpenttil@redhat.com>
Date:   Tue, 22 Mar 2022 06:35:43 +0200
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 v5] 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>
---
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
--- a/lib/test_hmm.c
+++ 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]);
+	mdevice->device.devt = dev;
+
+	ret = cdev_device_add(&mdevice->cdevice, &mdevice->device);
 	if (ret)
 		return ret;
 
@@ -1252,7 +1262,7 @@ 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