drm: omapdrm: dss: Support passing private data to debugfs show handlers

To simplify implementation of debugfs seq_file show handlers, the driver
passes the pointer to the show function through the debugfs_create_file
data pointer. This prevents using the pointer to pass driver private
data to the show handler, and requires all handlers to use global
variables to access private data.

To prepare for the removal of global private data in the driver, rework
the debugfs infrastructure to allow passing a private data pointer to
show handlers.

The price to pay is explicit removal of debugfs files to free the
internally allocated memory. This is desirable anyway as debugfs entries
should be removed when a component driver is unbound, otherwise crashes
will occur due to access to freed memory when the components will be
dynamically allocated instead of stored in global variables.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

1 files changed, 59 insertions, 30 deletions

diff --git a/drivers/gpu/drm/omapdrm/dss/dss.c b/drivers/gpu/drm/omapdrm/dss/dss.c
index 4b00faa1a8cc..14a86e2c6d83 100644
--- a/drivers/gpu/drm/omapdrm/dss/dss.c
+++ b/drivers/gpu/drm/omapdrm/dss/dss.c
@@ -365,14 +365,14 @@ static void dss_dump_clocks(struct dss_device *dss, struct seq_file *s)
 }
 #endif
 
-static void dss_dump_regs(struct seq_file *s)
+static int dss_dump_regs(struct seq_file *s, void *p)
 {
 	struct dss_device *dss = s->private;
 
 #define DUMPREG(dss, r) seq_printf(s, "%-35s %08x\n", #r, dss_read_reg(dss, r))
 
 	if (dss_runtime_get(dss))
-		return;
+		return 0;
 
 	DUMPREG(dss, DSS_REVISION);
 	DUMPREG(dss, DSS_SYSCONFIG);
@@ -387,6 +387,7 @@ static void dss_dump_regs(struct seq_file *s)
 
 	dss_runtime_put(dss);
 #undef DUMPREG
+	return 0;
 }
 
 static int dss_get_channel_index(enum omap_channel channel)
@@ -888,7 +889,7 @@ struct dss_device *dss_get_device(struct device *dev)
 
 /* DEBUGFS */
 #if defined(CONFIG_OMAP2_DSS_DEBUGFS)
-static void dss_debug_dump_clocks(struct seq_file *s)
+static int dss_debug_dump_clocks(struct seq_file *s, void *p)
 {
 	struct dss_device *dss = s->private;
 
@@ -897,28 +898,9 @@ static void dss_debug_dump_clocks(struct seq_file *s)
 #ifdef CONFIG_OMAP2_DSS_DSI
 	dsi_dump_clocks(s);
 #endif
-}
-
-static int dss_debug_show(struct seq_file *s, void *unused)
-{
-	void (*func)(struct seq_file *) = s->private;
-
-	func(s);
 	return 0;
 }
 
-static int dss_debug_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, dss_debug_show, inode->i_private);
-}
-
-static const struct file_operations dss_debug_fops = {
-	.open           = dss_debug_open,
-	.read           = seq_read,
-	.llseek         = seq_lseek,
-	.release        = single_release,
-};
-
 static struct dentry *dss_debugfs_dir;
 
 static int dss_initialize_debugfs(struct dss_device *dss)
@@ -931,9 +913,6 @@ static int dss_initialize_debugfs(struct dss_device *dss)
 		return err;
 	}
 
-	debugfs_create_file("clk", S_IRUGO, dss_debugfs_dir,
-			&dss_debug_dump_clocks, &dss_debug_fops);
-
 	return 0;
 }
 
@@ -943,15 +922,59 @@ static void dss_uninitialize_debugfs(void)
 		debugfs_remove_recursive(dss_debugfs_dir);
 }
 
-int dss_debugfs_create_file(const char *name, void (*write)(struct seq_file *))
+struct dss_debugfs_entry {
+	struct dentry *dentry;
+	int (*show_fn)(struct seq_file *s, void *data);
+	void *data;
+};
+
+static int dss_debug_open(struct inode *inode, struct file *file)
+{
+	struct dss_debugfs_entry *entry = inode->i_private;
+
+	return single_open(file, entry->show_fn, entry->data);
+}
+
+static const struct file_operations dss_debug_fops = {
+	.open		= dss_debug_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+struct dss_debugfs_entry *dss_debugfs_create_file(const char *name,
+		int (*show_fn)(struct seq_file *s, void *data), void *data)
 {
+	struct dss_debugfs_entry *entry;
 	struct dentry *d;
 
-	d = debugfs_create_file(name, S_IRUGO, dss_debugfs_dir,
-			write, &dss_debug_fops);
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return ERR_PTR(-ENOMEM);
+
+	entry->show_fn = show_fn;
+	entry->data = data;
 
-	return PTR_ERR_OR_ZERO(d);
+	d = debugfs_create_file(name, 0444, dss_debugfs_dir, entry,
+				&dss_debug_fops);
+	if (IS_ERR(d)) {
+		kfree(entry);
+		return ERR_PTR(PTR_ERR(d));
+	}
+
+	entry->dentry = d;
+	return entry;
+}
+
+void dss_debugfs_remove_file(struct dss_debugfs_entry *entry)
+{
+	if (IS_ERR_OR_NULL(entry))
+		return;
+
+	debugfs_remove(entry->dentry);
+	kfree(entry);
 }
+
 #else /* CONFIG_OMAP2_DSS_DEBUGFS */
 static inline int dss_initialize_debugfs(struct dss_device *dss)
 {
@@ -1449,7 +1472,9 @@ static int dss_probe(struct platform_device *pdev)
 	if (r)
 		goto err_pm_runtime_disable;
 
-	dss_debugfs_create_file("dss", dss_dump_regs);
+	dss->debugfs.clk = dss_debugfs_create_file("clk", dss_debug_dump_clocks,
+						   dss);
+	dss->debugfs.dss = dss_debugfs_create_file("dss", dss_dump_regs, dss);
 
 	/* Add all the child devices as components. */
 	device_for_each_child(&pdev->dev, &match, dss_add_child_component);
@@ -1461,6 +1486,8 @@ static int dss_probe(struct platform_device *pdev)
 	return 0;
 
 err_uninit_debugfs:
+	dss_debugfs_remove_file(dss->debugfs.clk);
+	dss_debugfs_remove_file(dss->debugfs.dss);
 	dss_uninitialize_debugfs();
 
 err_pm_runtime_disable:
@@ -1488,6 +1515,8 @@ static int dss_remove(struct platform_device *pdev)
 
 	component_master_del(&pdev->dev, &dss_component_ops);
 
+	dss_debugfs_remove_file(dss->debugfs.clk);
+	dss_debugfs_remove_file(dss->debugfs.dss);
 	dss_uninitialize_debugfs();
 
 	pm_runtime_disable(&pdev->dev);