fbdev: Move I/O read and write code into helper functions

Move the existing I/O read and write code for I/O memory into
the new helpers fb_cfb_read() and fb_cfb_write(). Make them the
default fp_ops. No functional changes.

In the near term, the new functions will be useful to the DRM
subsystem, which currently provides it's own implementation. It
can then use the shared code. In the longer term, it might make
sense to revise the I/O helper's default status and make them
opt-in by the driver. Systems that don't use them would not
contain the code any longer.

v2:
	* add detailed commit message (Javier)
	* rename fb_cfb_() to fb_io_() (Geert)
	* add fixes that got lost while moving the code (Geert)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Sui Jingfeng <suijingfeng@loongson.cn>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Helge Deller <deller@gmx.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230428122452.4856-19-tzimmermann@suse.de

3 files changed, 136 insertions, 117 deletions

diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile
index 08fabce76b74..8f0060160ffb 100644
--- a/drivers/video/fbdev/core/Makefile
+++ b/drivers/video/fbdev/core/Makefile
@@ -2,7 +2,7 @@
 obj-$(CONFIG_FB_NOTIFY)           += fb_notify.o
 obj-$(CONFIG_FB)                  += fb.o
 fb-y                              := fbmem.o fbmon.o fbcmap.o fbsysfs.o \
-                                     modedb.o fbcvt.o fb_cmdline.o
+                                     modedb.o fbcvt.o fb_cmdline.o fb_io_fops.o
 fb-$(CONFIG_FB_DEFERRED_IO)       += fb_defio.o
 
 ifeq ($(CONFIG_FRAMEBUFFER_CONSOLE),y)
diff --git a/drivers/video/fbdev/core/fb_io_fops.c b/drivers/video/fbdev/core/fb_io_fops.c
new file mode 100644
index 000000000000..f5299d50f33b
--- /dev/null
+++ b/drivers/video/fbdev/core/fb_io_fops.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/fb.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+ssize_t fb_io_read(struct fb_info *info, char __user *buf, size_t count, loff_t *ppos)
+{
+	unsigned long p = *ppos;
+	u8 *buffer, *dst;
+	u8 __iomem *src;
+	int c, cnt = 0, err = 0;
+	unsigned long total_size, trailing;
+
+	if (!info->screen_base)
+		return -ENODEV;
+
+	total_size = info->screen_size;
+
+	if (total_size == 0)
+		total_size = info->fix.smem_len;
+
+	if (p >= total_size)
+		return 0;
+
+	if (count >= total_size)
+		count = total_size;
+
+	if (count + p > total_size)
+		count = total_size - p;
+
+	buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
+			 GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	src = (u8 __iomem *) (info->screen_base + p);
+
+	if (info->fbops->fb_sync)
+		info->fbops->fb_sync(info);
+
+	while (count) {
+		c  = (count > PAGE_SIZE) ? PAGE_SIZE : count;
+		dst = buffer;
+		fb_memcpy_fromfb(dst, src, c);
+		dst += c;
+		src += c;
+
+		trailing = copy_to_user(buf, buffer, c);
+		if (trailing == c) {
+			err = -EFAULT;
+			break;
+		}
+		c -= trailing;
+
+		*ppos += c;
+		buf += c;
+		cnt += c;
+		count -= c;
+	}
+
+	kfree(buffer);
+
+	return cnt ? cnt : err;
+}
+EXPORT_SYMBOL(fb_io_read);
+
+ssize_t fb_io_write(struct fb_info *info, const char __user *buf, size_t count, loff_t *ppos)
+{
+	unsigned long p = *ppos;
+	u8 *buffer, *src;
+	u8 __iomem *dst;
+	int c, cnt = 0, err = 0;
+	unsigned long total_size, trailing;
+
+	if (!info->screen_base)
+		return -ENODEV;
+
+	total_size = info->screen_size;
+
+	if (total_size == 0)
+		total_size = info->fix.smem_len;
+
+	if (p > total_size)
+		return -EFBIG;
+
+	if (count > total_size) {
+		err = -EFBIG;
+		count = total_size;
+	}
+
+	if (count + p > total_size) {
+		if (!err)
+			err = -ENOSPC;
+
+		count = total_size - p;
+	}
+
+	buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
+			 GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	dst = (u8 __iomem *) (info->screen_base + p);
+
+	if (info->fbops->fb_sync)
+		info->fbops->fb_sync(info);
+
+	while (count) {
+		c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
+		src = buffer;
+
+		trailing = copy_from_user(src, buf, c);
+		if (trailing == c) {
+			err = -EFAULT;
+			break;
+		}
+		c -= trailing;
+
+		fb_memcpy_tofb(dst, src, c);
+		dst += c;
+		src += c;
+		*ppos += c;
+		buf += c;
+		cnt += c;
+		count -= c;
+	}
+
+	kfree(buffer);
+
+	return (cnt) ? cnt : err;
+}
+EXPORT_SYMBOL(fb_io_write);
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index bf5a0780457e..63af40831d7d 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -761,12 +761,7 @@ static struct fb_info *file_fb_info(struct file *file)
 static ssize_t
 fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 {
-	unsigned long p = *ppos;
 	struct fb_info *info = file_fb_info(file);
-	u8 *buffer, *dst;
-	u8 __iomem *src;
-	int c, cnt = 0, err = 0;
-	unsigned long total_size, trailing;
 
 	if (!info)
 		return -ENODEV;
@@ -777,67 +772,13 @@ fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 	if (info->fbops->fb_read)
 		return info->fbops->fb_read(info, buf, count, ppos);
 
-	if (!info->screen_base)
-		return -ENODEV;
-
-	total_size = info->screen_size;
-
-	if (total_size == 0)
-		total_size = info->fix.smem_len;
-
-	if (p >= total_size)
-		return 0;
-
-	if (count >= total_size)
-		count = total_size;
-
-	if (count + p > total_size)
-		count = total_size - p;
-
-	buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
-			 GFP_KERNEL);
-	if (!buffer)
-		return -ENOMEM;
-
-	src = (u8 __iomem *) (info->screen_base + p);
-
-	if (info->fbops->fb_sync)
-		info->fbops->fb_sync(info);
-
-	while (count) {
-		c  = (count > PAGE_SIZE) ? PAGE_SIZE : count;
-		dst = buffer;
-		fb_memcpy_fromfb(dst, src, c);
-		dst += c;
-		src += c;
-
-		trailing = copy_to_user(buf, buffer, c);
-		if (trailing == c) {
-			err = -EFAULT;
-			break;
-		}
-		c -= trailing;
-
-		*ppos += c;
-		buf += c;
-		cnt += c;
-		count -= c;
-	}
-
-	kfree(buffer);
-
-	return cnt ? cnt : err;
+	return fb_io_read(info, buf, count, ppos);
 }
 
 static ssize_t
 fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 {
-	unsigned long p = *ppos;
 	struct fb_info *info = file_fb_info(file);
-	u8 *buffer, *src;
-	u8 __iomem *dst;
-	int c, cnt = 0, err = 0;
-	unsigned long total_size, trailing;
 
 	if (!info)
 		return -ENODEV;
@@ -848,62 +789,7 @@ fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 	if (info->fbops->fb_write)
 		return info->fbops->fb_write(info, buf, count, ppos);
 
-	if (!info->screen_base)
-		return -ENODEV;
-
-	total_size = info->screen_size;
-
-	if (total_size == 0)
-		total_size = info->fix.smem_len;
-
-	if (p > total_size)
-		return -EFBIG;
-
-	if (count > total_size) {
-		err = -EFBIG;
-		count = total_size;
-	}
-
-	if (count + p > total_size) {
-		if (!err)
-			err = -ENOSPC;
-
-		count = total_size - p;
-	}
-
-	buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
-			 GFP_KERNEL);
-	if (!buffer)
-		return -ENOMEM;
-
-	dst = (u8 __iomem *) (info->screen_base + p);
-
-	if (info->fbops->fb_sync)
-		info->fbops->fb_sync(info);
-
-	while (count) {
-		c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
-		src = buffer;
-
-		trailing = copy_from_user(src, buf, c);
-		if (trailing == c) {
-			err = -EFAULT;
-			break;
-		}
-		c -= trailing;
-
-		fb_memcpy_tofb(dst, src, c);
-		dst += c;
-		src += c;
-		*ppos += c;
-		buf += c;
-		cnt += c;
-		count -= c;
-	}
-
-	kfree(buffer);
-
-	return (cnt) ? cnt : err;
+	return fb_io_write(info, buf, count, ppos);
 }
 
 int