[PATCH v2 10/10] efi: libstub: Simplify interfaces for primary_display

[Thomas Zimmermann <tzimmermann@suse.de>]

Rename alloc_primary_display() and __alloc_primary_display(), clarify
free semantics to make interfaces easier to understand.

Rename alloc_primary_display() to lookup_primary_display() as it
does not necessarily allocate. Then rename __alloc_primary_display()
to the new alloc_primary_display(). The helper belongs to
free_primary_display), so it should be named without underscores.

The lookup helper does not necessarily allocate, so the output
parameter needs_free to indicate when free should be called. Pass
an argument through the calls to track this state. Put the free
handling into release_primary_display() for simplificy.

Also move the comment fro primary_display.c to efi-stub-entry.c,
where it now describes lookup_primary_display().

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/firmware/efi/libstub/efi-stub-entry.c | 23 +++++++++++++++++--
 drivers/firmware/efi/libstub/efi-stub.c       | 22 ++++++++++++------
 drivers/firmware/efi/libstub/efistub.h        |  2 +-
 .../firmware/efi/libstub/primary_display.c    | 17 +-------------
 drivers/firmware/efi/libstub/zboot.c          |  6 +++--
 5 files changed, 42 insertions(+), 28 deletions(-)

diff --git a/drivers/firmware/efi/libstub/efi-stub-entry.c b/drivers/firmware/efi/libstub/efi-stub-entry.c
index aa85e910fe59..3077b51fe0b2 100644
--- a/drivers/firmware/efi/libstub/efi-stub-entry.c
+++ b/drivers/firmware/efi/libstub/efi-stub-entry.c
@@ -14,10 +14,29 @@ static void *kernel_image_addr(void *addr)
 	return addr + kernel_image_offset;
 }
 
-struct sysfb_display_info *alloc_primary_display(void)
+/*
+ * There are two ways of populating the core kernel's sysfb_primary_display
+ * via the stub:
+ *
+ *   - using a configuration table, which relies on the EFI init code to
+ *     locate the table and copy the contents; or
+ *
+ *   - by linking directly to the core kernel's copy of the global symbol.
+ *
+ * The latter is preferred because it makes the EFIFB earlycon available very
+ * early, but it only works if the EFI stub is part of the core kernel image
+ * itself. The zboot decompressor can only use the configuration table
+ * approach.
+ */
+
+struct sysfb_display_info *lookup_primary_display(bool *needs_free)
 {
+	*needs_free = true;
+
 	if (IS_ENABLED(CONFIG_ARM))
-		return __alloc_primary_display();
+		return alloc_primary_display();
+
+	*needs_free = false;
 
 	if (IS_ENABLED(CONFIG_X86) ||
 	    IS_ENABLED(CONFIG_EFI_EARLYCON) ||
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 42d6073bcd06..dc545f62c62b 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -51,14 +51,14 @@ static bool flat_va_mapping = (EFI_RT_VIRTUAL_OFFSET != 0);
 void __weak free_primary_display(struct sysfb_display_info *dpy)
 { }
 
-static struct sysfb_display_info *setup_primary_display(void)
+static struct sysfb_display_info *setup_primary_display(bool *dpy_needs_free)
 {
 	struct sysfb_display_info *dpy;
 	struct screen_info *screen = NULL;
 	struct edid_info *edid = NULL;
 	efi_status_t status;
 
-	dpy = alloc_primary_display();
+	dpy = lookup_primary_display(dpy_needs_free);
 	if (!dpy)
 		return NULL;
 	screen = &dpy->screen;
@@ -68,15 +68,22 @@ static struct sysfb_display_info *setup_primary_display(void)
 
 	status = efi_setup_graphics(screen, edid);
 	if (status != EFI_SUCCESS)
-		goto err_free_primary_display;
+		goto err___free_primary_display;
 
 	return dpy;
 
-err_free_primary_display:
-	free_primary_display(dpy);
+err___free_primary_display:
+	if (*dpy_needs_free)
+		free_primary_display(dpy);
 	return NULL;
 }
 
+static void release_primary_display(struct sysfb_display_info *dpy, bool dpy_needs_free)
+{
+	if (dpy && dpy_needs_free)
+		free_primary_display(dpy);
+}
+
 static void install_memreserve_table(void)
 {
 	struct linux_efi_memreserve *rsv;
@@ -156,13 +163,14 @@ efi_status_t efi_stub_common(efi_handle_t handle,
 			     char *cmdline_ptr)
 {
 	struct sysfb_display_info *dpy;
+	bool dpy_needs_free;
 	efi_status_t status;
 
 	status = check_platform_features();
 	if (status != EFI_SUCCESS)
 		return status;
 
-	dpy = setup_primary_display();
+	dpy = setup_primary_display(&dpy_needs_free);
 
 	efi_retrieve_eventlog();
 
@@ -182,7 +190,7 @@ efi_status_t efi_stub_common(efi_handle_t handle,
 
 	status = efi_boot_kernel(handle, image, image_addr, cmdline_ptr);
 
-	free_primary_display(dpy);
+	release_primary_display(dpy, dpy_needs_free);
 
 	return status;
 }
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 979a21818cc1..1503ffb82903 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1176,8 +1176,8 @@ efi_enable_reset_attack_mitigation(void) { }
 
 void efi_retrieve_eventlog(void);
 
+struct sysfb_display_info *lookup_primary_display(bool *needs_free);
 struct sysfb_display_info *alloc_primary_display(void);
-struct sysfb_display_info *__alloc_primary_display(void);
 void free_primary_display(struct sysfb_display_info *dpy);
 
 void efi_cache_sync_image(unsigned long image_base,
diff --git a/drivers/firmware/efi/libstub/primary_display.c b/drivers/firmware/efi/libstub/primary_display.c
index cdaebab26514..34c54ac1e02a 100644
--- a/drivers/firmware/efi/libstub/primary_display.c
+++ b/drivers/firmware/efi/libstub/primary_display.c
@@ -7,24 +7,9 @@
 
 #include "efistub.h"
 
-/*
- * There are two ways of populating the core kernel's sysfb_primary_display
- * via the stub:
- *
- *   - using a configuration table, which relies on the EFI init code to
- *     locate the table and copy the contents; or
- *
- *   - by linking directly to the core kernel's copy of the global symbol.
- *
- * The latter is preferred because it makes the EFIFB earlycon available very
- * early, but it only works if the EFI stub is part of the core kernel image
- * itself. The zboot decompressor can only use the configuration table
- * approach.
- */
-
 static efi_guid_t primary_display_guid = LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID;
 
-struct sysfb_display_info *__alloc_primary_display(void)
+struct sysfb_display_info *alloc_primary_display(void)
 {
 	struct sysfb_display_info *dpy;
 	efi_status_t status;
diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
index 4b76f74c56da..c1fd1fdbcb08 100644
--- a/drivers/firmware/efi/libstub/zboot.c
+++ b/drivers/firmware/efi/libstub/zboot.c
@@ -26,9 +26,11 @@ void __weak efi_cache_sync_image(unsigned long image_base,
 	// executable code loaded into memory to be safe for execution.
 }
 
-struct sysfb_display_info *alloc_primary_display(void)
+struct sysfb_display_info *lookup_primary_display(bool *needs_free)
 {
-	return __alloc_primary_display();
+	*needs_free = true;
+
+	return alloc_primary_display();
 }
 
 asmlinkage efi_status_t __efiapi
-- 
2.51.1