[RESEND RFC PATCH 2/5] firmware: sysfb: Add helpers to unregister a pdev and disable registration

[Javier Martinez Canillas]

These can be used by subsystems to unregister a platform device registered
by sysfb and also to disable future platform device registration in sysfb.

Suggested-by: Daniel Vetter <daniel.vet...@ffwll.ch>
Signed-off-by: Javier Martinez Canillas <javi...@redhat.com>
---

 drivers/firmware/sysfb.c | 47 +++++++++++++++++++++++++++++++++++-----
 include/linux/sysfb.h    | 19 ++++++++++++++++
 2 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c
index b032f40a92de..08ae78c083f1 100644
--- a/drivers/firmware/sysfb.c
+++ b/drivers/firmware/sysfb.c
@@ -34,21 +34,52 @@
 #include <linux/screen_info.h>
 #include <linux/sysfb.h>
 
+static struct platform_device *pd;
+static DEFINE_MUTEX(load_lock);
+static bool disabled;
+
+void sysfb_disable(void)
+{
+       mutex_lock(&load_lock);
+       disabled = true;
+       mutex_unlock(&load_lock);
+}
+EXPORT_SYMBOL_GPL(sysfb_disable);
+
+bool sysfb_try_unregister(struct device *dev)
+{
+       bool ret = true;
+
+       mutex_lock(&load_lock);
+       if (!pd || pd != to_platform_device(dev))
+               return false;
+
+       platform_device_unregister(to_platform_device(dev));
+       pd = NULL;
+       mutex_unlock(&load_lock);
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(sysfb_try_unregister);
+
 static __init int sysfb_init(void)
 {
        struct screen_info *si = &screen_info;
        struct simplefb_platform_data mode;
-       struct platform_device *pd;
        const char *name;
        bool compatible;
-       int ret;
+       int ret = 0;
+
+       mutex_lock(&load_lock);
+       if (disabled)
+               goto unlock_mutex;
 
        /* try to create a simple-framebuffer device */
        compatible = sysfb_parse_mode(si, &mode);
        if (compatible) {
                pd = sysfb_create_simplefb(si, &mode);
                if (!IS_ERR(pd))
-                       return 0;
+                       goto unlock_mutex;
        }
 
        /* if the FB is incompatible, create a legacy framebuffer device */
@@ -60,8 +91,10 @@ static __init int sysfb_init(void)
                name = "platform-framebuffer";
 
        pd = platform_device_alloc(name, 0);
-       if (!pd)
-               return -ENOMEM;
+       if (!pd) {
+               ret = -ENOMEM;
+               goto unlock_mutex;
+       }
 
        sysfb_apply_efi_quirks(pd);
 
@@ -73,9 +106,11 @@ static __init int sysfb_init(void)
        if (ret)
                goto err;
 
-       return 0;
+       goto unlock_mutex;
 err:
        platform_device_put(pd);
+unlock_mutex:
+       mutex_unlock(&load_lock);
        return ret;
 }
 
diff --git a/include/linux/sysfb.h b/include/linux/sysfb.h
index 708152e9037b..e8c0313fac8f 100644
--- a/include/linux/sysfb.h
+++ b/include/linux/sysfb.h
@@ -55,6 +55,25 @@ struct efifb_dmi_info {
        int flags;
 };
 
+#ifdef CONFIG_SYSFB
+
+void sysfb_disable(void);
+bool sysfb_try_unregister(struct device *dev);
+
+#else /* CONFIG_SYSFB */
+
+static inline void sysfb_disable(void)
+{
+
+}
+
+static inline bool sysfb_try_unregister(struct device *dev)
+{
+       return false;
+}
+
+#endif /* CONFIG_SYSFB */
+
 #ifdef CONFIG_EFI
 
 extern struct efifb_dmi_info efifb_dmi_list[];
-- 
2.35.1