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SubjectRe: [RFC PATCH 1/3] ACPI: scan: add userland notification while handling eject events
On Fri, Mar 27, 2020 at 07:22:45PM +0800, Chester Lin wrote:
> Add a request_offline attribute in order to tell the kernel if it's
> required to send notifications to userland first while handling an eject
> event. Userland will have to put the target device offline when this
> attribute is set.
>
> Signed-off-by: Chester Lin <clin@suse.com>
> ---
> Documentation/ABI/testing/sysfs-bus-acpi | 16 ++++++++++
> drivers/acpi/device_sysfs.c | 40 +++++++++++++++++++++++-
> drivers/acpi/scan.c | 39 +++++++++++++++++++----
> include/acpi/acpi_bus.h | 1 +
> 4 files changed, 89 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-acpi b/Documentation/ABI/testing/sysfs-bus-acpi
> index e7898cfe5fb1..b9c467704889 100644
> --- a/Documentation/ABI/testing/sysfs-bus-acpi
> +++ b/Documentation/ABI/testing/sysfs-bus-acpi
> @@ -93,3 +93,19 @@ Description:
> hardware, if the _HRV control method is present. It is mostly
> useful for non-PCI devices because lspci can list the hardware
> version for PCI devices.
> +
> +What: /sys/bus/acpi/devices/.../request_offline
> +Date: Mar, 2020
> +Contact: Chester Lin <clin@suse.com>
> +Description:
> + (RW) Allows the userland to receive offline requests when
> + devices are planning to be ejected.
> +
> + If bit [0] is clear, the kernel will automatically try putting
> + the target offline before the target can be ejected.
> +
> + If bit [0] is set, a uevent will be sent to userland as an
> + offline request and userland is responsible for handling offline
> + operations before the target can be ejected. This approach
> + provides flexibility while some applications could need more
> + time to release resources.

Don't use "bit", use 1/0/y/n/Y/N as the kernel will parse all of that
for you with the kstrtobool() which was created just for this type of
sysfs file.

> diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
> index 96869f1538b9..453bd1b9edf5 100644
> --- a/drivers/acpi/device_sysfs.c
> +++ b/drivers/acpi/device_sysfs.c
> @@ -506,6 +506,37 @@ static ssize_t status_show(struct device *dev, struct device_attribute *attr,
> }
> static DEVICE_ATTR_RO(status);
>
> +static ssize_t request_offline_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct acpi_device *acpi_dev = to_acpi_device(dev);
> +
> + return sprintf(buf, "%u\n", acpi_dev->request_offline?1:0);
> +}
> +
> +static ssize_t request_offline_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t count)
> +{
> + struct acpi_device *acpi_dev = to_acpi_device(dev);
> +
> + if (!count)
> + return -EINVAL;
> +
> + switch (buf[0]) {
> + case '0':
> + acpi_dev->request_offline = false;
> + break;
> + case '1':
> + acpi_dev->request_offline = true;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return count;
> +}
> +static DEVICE_ATTR_RW(request_offline);
> +
> /**
> * acpi_device_setup_files - Create sysfs attributes of an ACPI device.
> * @dev: ACPI device object.
> @@ -580,6 +611,11 @@ int acpi_device_setup_files(struct acpi_device *dev)
> result = device_create_file(&dev->dev, &dev_attr_eject);
> if (result)
> return result;
> +
> + result = device_create_file(&dev->dev,
> + &dev_attr_request_offline);
> + if (result)
> + return result;
> }
>
> if (dev->flags.power_manageable) {
> @@ -623,8 +659,10 @@ void acpi_device_remove_files(struct acpi_device *dev)
> /*
> * If device has _EJ0, remove 'eject' file.
> */
> - if (acpi_has_method(dev->handle, "_EJ0"))
> + if (acpi_has_method(dev->handle, "_EJ0")) {
> device_remove_file(&dev->dev, &dev_attr_eject);
> + device_remove_file(&dev->dev, &dev_attr_request_offline);

You all really should be using an attribute group and the is_visible()
callback to handle all of this for you automatically.

But that's a separate issue than this specific patch.

> + }
>
> if (acpi_has_method(dev->handle, "_SUN"))
> device_remove_file(&dev->dev, &dev_attr_sun);
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 6d3448895382..1cb39c5360cf 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -145,6 +145,7 @@ static acpi_status acpi_bus_offline(acpi_handle handle, u32 lvl, void *data,
> struct acpi_device_physical_node *pn;
> bool second_pass = (bool)data;
> acpi_status status = AE_OK;
> + char *envp[] = { "EVENT=offline", NULL };
>
> if (acpi_bus_get_device(handle, &device))
> return AE_OK;
> @@ -166,7 +167,18 @@ static acpi_status acpi_bus_offline(acpi_handle handle, u32 lvl, void *data,
> } else {
> pn->put_online = false;
> }
> - ret = device_offline(pn->dev);
> +
> + /* Don't offline directly but need to notify userland first */
> + if (device->request_offline) {
> + if (pn->dev->offline)
> + ret = 0;
> + else
> + ret = kobject_uevent_env(&pn->dev->kobj,
> + KOBJ_CHANGE, envp);

So this is a userspace visable change with regards to kobject events?

Are you sure that is ok?


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