Messages in this thread Patch in this message | | | Subject | Re: [PATCH -next 3/4] spi: mockup: Add runtime device tree overlay interface | From | "weiyongjun (A)" <> | Date | Tue, 30 Aug 2022 11:05:44 +0800 |
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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@huawei.com> >> --- >> 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) { >
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