[PATCH v2 5/5] apple-gmux: add debugfs interface

Orlando Chamberlain
2023-02-16T12:25:46Z

Allow reading and writing gmux ports from userspace.

For example:

echo 4 > /sys/kernel/debug/apple_gmux/selected_port
cat /sys/kernel/debug/apple_gmux/selected_port_data | xxd -p

Will show the gmux version information (00000005 in this case)

Signed-off-by: Orlando Chamberlain <orlandoch.dev@gmail.com>
---
v1->v2: Use debugfs instead of sysfs.
drivers/platform/x86/apple-gmux.c | 88 +++++++++++++++++++++++++++++++
1 file changed, 88 insertions(+)

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 5bac6dcfada0..e8a35d98b113 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -22,6 +22,7 @@
#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/vga_switcheroo.h>
+#include <linux/debugfs.h>
#include <asm/io.h>

/**
@@ -66,6 +67,10 @@ struct apple_gmux_data {
enum vga_switcheroo_client_id switch_state_external;
enum vga_switcheroo_state power_state;
struct completion powerchange_done;
+
+ /* debugfs data */
+ u8 selected_port;
+ struct dentry *debug_dentry;
};

static struct apple_gmux_data *apple_gmux_data;
@@ -674,6 +679,87 @@ static void gmux_notify_handler(acpi_handle device, u32 value, void *context)
complete(&gmux_data->powerchange_done);
}

+/**
+ * DOC: Debugfs Interface
+ *
+ * gmux ports can be accessed from userspace as a debugfs interface. For example:
+ *
+ * # echo 4 > /sys/kernel/debug/apple_gmux/selected_port
+ * # cat /sys/kernel/debug/apple_gmux/selected_port_data | xxd -p
+ * 00000005
+ *
+ * Reads 4 bytes from port 4 (GMUX_PORT_VERSION_MAJOR).
+ *
+ * 1 and 4 byte writes are also allowed.
+ */
+
+static ssize_t gmux_selected_port_data_write(struct file *file,
+ const char __user *userbuf, size_t count, loff_t *ppos)
+{
+ struct apple_gmux_data *gmux_data = file->private_data;
+ int ret;
+
+ if (*ppos)
+ return -EINVAL;
+
+ if (count == 1) {
+ u8 data;
+
+ ret = copy_from_user(&data, userbuf, 1);
+ if (ret)
+ return ret;
+ gmux_write8(gmux_data, gmux_data->selected_port, data);
+ } else if (count == 4) {
+ u32 data;
+
+ ret = copy_from_user(&data, userbuf, 4);
+ if (ret)
+ return ret;
+ gmux_write32(gmux_data, gmux_data->selected_port, data);
+ } else
+ return -EINVAL;
+
+ return count;
+}
+
+static ssize_t gmux_selected_port_data_read(struct file *file,
+ char __user *userbuf, size_t count, loff_t *ppos)
+{
+ struct apple_gmux_data *gmux_data = file->private_data;
+ u32 data;
+
+ data = gmux_read32(gmux_data, gmux_data->selected_port);
+
+ return simple_read_from_buffer(userbuf, count, ppos, &data, sizeof(data));
+}
+
+static const struct file_operations gmux_port_data_ops = {
+ .open = simple_open,
+ .write = gmux_selected_port_data_write,
+ .read = gmux_selected_port_data_read
+};
+
+static void gmux_init_debugfs(struct apple_gmux_data *gmux_data)
+{
+ struct dentry *debug_dentry;
+
+ debug_dentry = debugfs_create_dir(KBUILD_MODNAME, NULL);
+
+ if (IS_ERR(debug_dentry))
+ return;
+
+ gmux_data->debug_dentry = debug_dentry;
+
+ debugfs_create_u8("selected_port", 0644, debug_dentry, &gmux_data->selected_port);
+ debugfs_create_file("selected_port_data", 0644, debug_dentry,
+ gmux_data, &gmux_port_data_ops);
+}
+
+static void gmux_fini_debugfs(struct apple_gmux_data *gmux_data)
+{
+ debugfs_remove_recursive(gmux_data->debug_dentry);
+}
+
static int gmux_suspend(struct device *dev)
{
struct pnp_dev *pnp = to_pnp_dev(dev);
@@ -874,6 +960,7 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
goto err_register_handler;
}

+ gmux_init_debugfs(gmux_data);
return 0;

err_register_handler:
@@ -905,6 +992,7 @@ static void gmux_remove(struct pnp_dev *pnp)
{
struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

+ gmux_fini_debugfs(gmux_data);
vga_switcheroo_unregister_handler();
gmux_disable_interrupts(gmux_data);
if (gmux_data->gpe >= 0) {
--
2.39.1