On 2022/8/30 5:29, Frank Rowand wrote:
comment inline below, plus adding to cc: and to: list
On 8/26/22 09:43, Wei Yongjun wrote:
Add a runtime device tree overlay interface for device need dts file.
With it its possible to use device tree overlays without having to use
a per-platform overlay manager.
Why is an overlay needed? The documentation in patch 4 shows providing
a dtb as an argument to the qemu-system-x86_64 command, which should be
sufficient to supply the appropriate dtb.
Fist, we are aimed to build a device driver regression testsuit. Without
overlay, lots of the dtb fragments must be combined to a very big one, it
may different to maintainence. overlay makes easily to attach/detech as
the device's requirement.
Seconds, overlay dts may be used to found or verification issues related
to of_node_put or others, such as patches like:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/?qt=grep&q=node_put
many of them may found by static check tool, which may leak of tesing.
The documentation I post does not use overlay dts, but when overlay
dts[1] is used, we can found the of node leak:
$ python3 -m kddv.cmds.mock -b spi -d mchp23k256
create spi device mchp23k256 success!
$ ls /sys/bus/spi/drivers/mchp23k256/spi0.0/mtd/
mtd0 mtd0ro
$ python3 -m kddv.cmds.mock -b spi -d mchp23k256 -r
[ 233.508565] Deleting MTD partitions on "spi0.0":
[ 233.516784] OF: ERROR: memory leak, expected refcount 1 instead of 2,
of_node_get()/of_node_put() unbalanced - destroy cset entry: attach
overlay node /spi/spi-sram@0
remove spi device mchp23k256 success!
Not sure it is worth to fix issues like this, but at least, we can
tesing them now.
-[1]---------------------------------------------------------
/dts-v1/;
/plugin/;
&{/spi} {
spi-sram@0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "microchip,mchp23k256";
reg = <0>;
spi-max-frequency = <20000000>;
};
};
-------------------------------------------------------
Regards,
Wei Yongjun
-Frank
Add a new device by command:
$ cat test.dtbo > /sys/class/spi_master/spi0/overlay_fdto
Remove the device by command:
$ echo remove > /sys/class/spi_master/spi0/overlay_fdto
Signed-off-by: Wei Yongjun <weiyongjun1@xxxxxxxxxx>
---
drivers/spi/Kconfig | 2 ++
drivers/spi/spi-mockup.c | 48 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index e0f0fa2746ad..4b7c84ddb367 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -1161,6 +1161,8 @@ config SPI_TLE62X0
config SPI_MOCKUP
tristate "SPI controller Testing Driver"
depends on OF
+ select OF_EARLY_FLATTREE
+ select OF_RESOLVE
select BPF_EVENTS
help
This enables SPI controller testing driver, which provides a way to
diff --git a/drivers/spi/spi-mockup.c b/drivers/spi/spi-mockup.c
index 7a93b194ee53..404ad821bf6a 100644
--- a/drivers/spi/spi-mockup.c
+++ b/drivers/spi/spi-mockup.c
@@ -21,6 +21,9 @@
struct mockup_spi {
struct mutex lock;
struct spi_device *devs[MOCKUP_CHIPSELECT_MAX];
+
+ void *fdto;
+ int ovcs_id;
};
static struct spi_master *to_spi_master(struct device *dev)
@@ -145,9 +148,53 @@ delete_device_store(struct device *dev, struct device_attribute *attr,
}
static DEVICE_ATTR_WO(delete_device);
+static ssize_t
+overlay_fdto_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct spi_master *master = to_spi_master(dev);
+ struct mockup_spi *mock = spi_master_get_devdata(master);
+ int ret;
+
+ mutex_lock(&mock->lock);
+
+ if (strncmp(buf, "remove\n", count) == 0) {
+ if (mock->ovcs_id < 0) {
+ ret = -ENOENT;
+ goto out_unlock;
+ }
+ of_overlay_remove(&mock->ovcs_id);
+ kfree(mock->fdto);
+ mock->ovcs_id = -1;
+ mock->fdto = NULL;
+ } else {
+ if (mock->ovcs_id >= 0) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ mock->fdto = kmemdup(buf, count, GFP_KERNEL);
+ if (!mock->fdto) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+ ret = of_overlay_fdt_apply(mock->fdto, count, &mock->ovcs_id);
+ if (ret < 0)
+ goto out_unlock;
+ }
+
+ mutex_unlock(&mock->lock);
+ return count;
+
+out_unlock:
+ mutex_unlock(&mock->lock);
+ return ret;
+}
+static DEVICE_ATTR_WO(overlay_fdto);
+
static struct attribute *spi_mockup_attrs[] = {
&dev_attr_new_device.attr,
&dev_attr_delete_device.attr,
+ &dev_attr_overlay_fdto.attr,
NULL
};
ATTRIBUTE_GROUPS(spi_mockup);
@@ -227,6 +274,7 @@ static int spi_mockup_probe(struct platform_device *pdev)
mock = spi_master_get_devdata(master);
mutex_init(&mock->lock);
+ mock->ovcs_id = -1;
ret = spi_register_master(master);
if (ret) {
