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Message-ID: <3e6c6cba-ad53-d380-a028-840fb19dbfcb@redhat.com>
Date: Fri, 10 Feb 2023 21:15:50 +0100
From: Hans de Goede <hdegoede@...hat.com>
To: Orlando Chamberlain <orlandoch.dev@...il.com>,
platform-driver-x86@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, alsa-devel@...a-project.org
Cc: Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
"Pan, Xinhui" <Xinhui.Pan@....com>,
David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>,
Mark Gross <markgross@...nel.org>,
Jaroslav Kysela <perex@...ex.cz>,
Takashi Iwai <tiwai@...e.com>,
Hawking Zhang <Hawking.Zhang@....com>,
Andrey Grodzovsky <andrey.grodzovsky@....com>,
Lijo Lazar <lijo.lazar@....com>,
YiPeng Chai <YiPeng.Chai@....com>,
Somalapuram Amaranath <Amaranath.Somalapuram@....com>,
Mario Limonciello <mario.limonciello@....com>,
Bokun Zhang <Bokun.Zhang@....com>,
Jack Xiao <Jack.Xiao@....com>,
Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
Rander Wang <rander.wang@...el.com>,
Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
Amadeusz Sławiński
<amadeuszx.slawinski@...ux.intel.com>,
Yong Zhi <yong.zhi@...el.com>, Evan Quan <evan.quan@....com>,
Kerem Karabay <kekrby@...il.com>,
Aditya Garg <gargaditya08@...e.com>,
Aun-Ali Zaidi <admin@...eit.net>
Subject: Re: [RFC PATCH 7/9] apple-gmux: add sysfs interface
Hi,
On 2/10/23 05:48, Orlando Chamberlain wrote:
> Allow reading gmux ports from userspace. When the unsafe module
> parameter allow_user_writes is true, writing 1 byte
> values is also allowed.
>
> For example:
>
> cd /sys/bus/acpi/devices/APP000B:00/physical_node/
> echo 4 > gmux_selected_port
> cat gmux_selected_port_data | xxd -p
>
> Will show the gmux version information (00000005 in this case)
Please use debugfs for this and as part of the conversion
drop the #ifdef-s (debugfs has stubs for when not enabled)
and drop all the error checking of creating the files, debugfs
is deliberately designed to not have any error checking in
the setup / teardown code.
This also removes the need for the allow_user_writes parameter
replacing it with the new kernel lockdown mechanism. debugfs
will automatically block access to writable files when
the kernel is in lockdown mode.
Regards,
Hans
> Signed-off-by: Orlando Chamberlain <orlandoch.dev@...il.com>
> ---
> drivers/platform/x86/apple-gmux.c | 129 ++++++++++++++++++++++++++++++
> 1 file changed, 129 insertions(+)
>
> diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
> index c38d6ef0c15a..756059d48393 100644
> --- a/drivers/platform/x86/apple-gmux.c
> +++ b/drivers/platform/x86/apple-gmux.c
> @@ -66,6 +66,11 @@ struct apple_gmux_data {
> enum vga_switcheroo_client_id switch_state_external;
> enum vga_switcheroo_state power_state;
> struct completion powerchange_done;
> +
> +#ifdef CONFIG_SYSFS
> + /* sysfs data */
> + int selected_port;
> +#endif /* CONFIG_SYSFS */
> };
>
> static struct apple_gmux_data *apple_gmux_data;
> @@ -651,6 +656,121 @@ static void gmux_notify_handler(acpi_handle device, u32 value, void *context)
> complete(&gmux_data->powerchange_done);
> }
>
> +/**
> + * DOC: Sysfs Interface
> + *
> + * gmux ports can be read from userspace as a sysfs interface. For example:
> + *
> + * # echo 4 > /sys/bus/acpi/devices/APP000B:00/physical_node/gmux_selected_port
> + * # cat /sys/bus/acpi/devices/APP000B:00/physical_node/gmux_selected_port_data | xxd -p
> + * 00000005
> + *
> + * Reads 4 bytes from port 4 (GMUX_PORT_VERSION_MAJOR).
> + *
> + * Single byte writes are also supported, however this must be enabled with the
> + * unsafe allow_user_writes module parameter.
> + *
> + */
> +
> +#ifdef CONFIG_SYSFS
> +
> +static bool allow_user_writes;
> +module_param_unsafe(allow_user_writes, bool, 0);
> +MODULE_PARM_DESC(allow_user_writes, "Allow userspace to write to gmux ports (default: false) (bool)");
> +
> +static ssize_t gmux_selected_port_store(struct device *dev,
> + struct device_attribute *attr, const char *sysfsbuf, size_t count)
> +{
> + struct apple_gmux_data *gmux_data = dev_get_drvdata(dev);
> + u8 port;
> +
> + if (kstrtou8(sysfsbuf, 10, &port) < 0)
> + return -EINVAL;
> +
> + /* On pio gmux's, make sure the user doesn't access too high of a port. */
> + if ((gmux_data->config == &apple_gmux_pio) &&
> + port > (gmux_data->iolen - 4))
> + return -EINVAL;
> +
> + gmux_data->selected_port = port;
> + return count;
> +}
> +
> +static ssize_t gmux_selected_port_show(struct device *dev,
> + struct device_attribute *attr, char *sysfsbuf)
> +{
> + struct apple_gmux_data *gmux_data = dev_get_drvdata(dev);
> +
> + return sysfs_emit(sysfsbuf, "%d\n", gmux_data->selected_port);
> +}
> +
> +DEVICE_ATTR_RW(gmux_selected_port);
> +
> +static ssize_t gmux_selected_port_data_store(struct device *dev,
> + struct device_attribute *attr, const char *sysfsbuf, size_t count)
> +{
> + struct apple_gmux_data *gmux_data = dev_get_drvdata(dev);
> +
> + if (count == 1)
> + gmux_write8(gmux_data, gmux_data->selected_port, *sysfsbuf);
> + else
> + return -EINVAL;
> +
> + return count;
> +}
> +
> +static ssize_t gmux_selected_port_data_show(struct device *dev,
> + struct device_attribute *attr, char *sysfsbuf)
> +{
> + struct apple_gmux_data *gmux_data = dev_get_drvdata(dev);
> + u32 data;
> +
> + data = gmux_read32(gmux_data, gmux_data->selected_port);
> + memcpy(sysfsbuf, &data, sizeof(data));
> +
> + return sizeof(data);
> +}
> +
> +struct device_attribute dev_attr_gmux_selected_port_data_rw = __ATTR_RW(gmux_selected_port_data);
> +struct device_attribute dev_attr_gmux_selected_port_data_ro = __ATTR_RO(gmux_selected_port_data);
> +
> +static int gmux_init_sysfs(struct pnp_dev *pnp)
> +{
> + int ret;
> +
> + ret = device_create_file(&pnp->dev, &dev_attr_gmux_selected_port);
> + if (ret)
> + return ret;
> + if (allow_user_writes)
> + ret = device_create_file(&pnp->dev, &dev_attr_gmux_selected_port_data_rw);
> + else
> + ret = device_create_file(&pnp->dev, &dev_attr_gmux_selected_port_data_ro);
> + if (ret)
> + device_remove_file(&pnp->dev, &dev_attr_gmux_selected_port);
> + return ret;
> +}
> +
> +static void gmux_fini_sysfs(struct pnp_dev *pnp)
> +{
> + device_remove_file(&pnp->dev, &dev_attr_gmux_selected_port);
> + if (allow_user_writes)
> + device_remove_file(&pnp->dev, &dev_attr_gmux_selected_port_data_rw);
> + else
> + device_remove_file(&pnp->dev, &dev_attr_gmux_selected_port_data_ro);
> +}
> +
> +#else
> +
> +static int gmux_init_sysfs(struct pnp_dev *pnp)
> +{
> + return 0;
> +}
> +static void gmux_fini_sysfs(struct pnp_dev *pnp)
> +{
> +}
> +
> +#endif /* CONFIG_SYSFS */
> +
> static int gmux_suspend(struct device *dev)
> {
> struct pnp_dev *pnp = to_pnp_dev(dev);
> @@ -846,8 +966,16 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
> goto err_register_handler;
> }
>
> + ret = gmux_init_sysfs(pnp);
> + if (ret) {
> + pr_err("Failed to register gmux sysfs entries\n");
> + goto err_sysfs;
> + }
> +
> return 0;
>
> +err_sysfs:
> + vga_switcheroo_unregister_handler();
> err_register_handler:
> gmux_disable_interrupts(gmux_data);
> apple_gmux_data = NULL;
> @@ -877,6 +1005,7 @@ static void gmux_remove(struct pnp_dev *pnp)
> {
> struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);
>
> + gmux_fini_sysfs(pnp);
> vga_switcheroo_unregister_handler();
> gmux_disable_interrupts(gmux_data);
> if (gmux_data->gpe >= 0) {
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