[PATCH 5.15 124/167] firmware: sysfb: Add sysfb_disable() helper function

Greg Kroah-Hartman
2022-07-19T12:41:49Z

From: Javier Martinez Canillas <javierm@redhat.com>

[ Upstream commit bde376e9de3c0bc55eedc8956b0f114c05531595 ]

This 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.vetter@ffwll.ch>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220607182338.344270-3-javierm@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../driver-api/firmware/other_interfaces.rst | 6 +++
drivers/firmware/sysfb.c | 54 ++++++++++++++++---
include/linux/sysfb.h | 12 +++++
3 files changed, 66 insertions(+), 6 deletions(-)

diff --git a/Documentation/driver-api/firmware/other_interfaces.rst b/Documentation/driver-api/firmware/other_interfaces.rst
index b81794e0cfbb..06ac89adaafb 100644
--- a/Documentation/driver-api/firmware/other_interfaces.rst
+++ b/Documentation/driver-api/firmware/other_interfaces.rst
@@ -13,6 +13,12 @@ EDD Interfaces
.. kernel-doc:: drivers/firmware/edd.c
:internal:

+Generic System Framebuffers Interface
+-------------------------------------
+
+.. kernel-doc:: drivers/firmware/sysfb.c
+ :export:
+
Intel Stratix10 SoC Service Layer
---------------------------------
Some features of the Intel Stratix10 SoC require a level of privilege
diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c
index b032f40a92de..1f276f108cc9 100644
--- a/drivers/firmware/sysfb.c
+++ b/drivers/firmware/sysfb.c
@@ -34,21 +34,59 @@
#include <linux/screen_info.h>
#include <linux/sysfb.h>

+static struct platform_device *pd;
+static DEFINE_MUTEX(disable_lock);
+static bool disabled;
+
+static bool sysfb_unregister(void)
+{
+ if (IS_ERR_OR_NULL(pd))
+ return false;
+
+ platform_device_unregister(pd);
+ pd = NULL;
+
+ return true;
+}
+
+/**
+ * sysfb_disable() - disable the Generic System Framebuffers support
+ *
+ * This disables the registration of system framebuffer devices that match the
+ * generic drivers that make use of the system framebuffer set up by firmware.
+ *
+ * It also unregisters a device if this was already registered by sysfb_init().
+ *
+ * Context: The function can sleep. A @disable_lock mutex is acquired to serialize
+ * against sysfb_init(), that registers a system framebuffer device.
+ */
+void sysfb_disable(void)
+{
+ mutex_lock(&disable_lock);
+ sysfb_unregister();
+ disabled = true;
+ mutex_unlock(&disable_lock);
+}
+EXPORT_SYMBOL_GPL(sysfb_disable);
+
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(&disable_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 +98,10 @@ 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 +113,11 @@ static __init int sysfb_init(void)
if (ret)
goto err;

- return 0;
+ goto unlock_mutex;
err:
platform_device_put(pd);
+unlock_mutex:
+ mutex_unlock(&disable_lock);
return ret;
}

diff --git a/include/linux/sysfb.h b/include/linux/sysfb.h
index 708152e9037b..8ba8b5be5567 100644
--- a/include/linux/sysfb.h
+++ b/include/linux/sysfb.h
@@ -55,6 +55,18 @@ struct efifb_dmi_info {
int flags;
};

+#ifdef CONFIG_SYSFB
+
+void sysfb_disable(void);
+
+#else /* CONFIG_SYSFB */
+
+static inline void sysfb_disable(void)
+{
+}
+
+#endif /* CONFIG_SYSFB */
+
#ifdef CONFIG_EFI

extern struct efifb_dmi_info efifb_dmi_list[];
--
2.35.1