platform/x86: apple-gmux: add debugfs interface

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)

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Orlando Chamberlain <orlandoch.dev@gmail.com>
Link: https://lore.kernel.org/r/20230303112842.3094-5-orlandoch.dev@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 59c4ee8109dd915b3ce6707e20c6092d43e7cddd..757fd71c900f12b49f48eee59035198ee713ab3f 100644 (file)
--- 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>
 
 /**
@@ -73,6 +74,10 @@ 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;
@@ -670,6 +675,81 @@ 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)
+{
+       gmux_data->debug_dentry = debugfs_create_dir(KBUILD_MODNAME, NULL);
+
+       debugfs_create_u8("selected_port", 0644, gmux_data->debug_dentry,
+                       &gmux_data->selected_port);
+       debugfs_create_file("selected_port_data", 0644, gmux_data->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);
@@ -870,6 +950,7 @@ get_version:
                goto err_register_handler;
        }
 
+       gmux_init_debugfs(gmux_data);
        return 0;
 
 err_register_handler:
@@ -901,6 +982,7 @@ 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) {