drivers/video/fbdev/core/fb_sys_fops.c

File Facts

System

Linux kernel

Corpus path

drivers/video/fbdev/core/fb_sys_fops.c

Extension

.c

Size

2304 bytes

Lines

117

Domain

Driver Families

Bucket

drivers/video

Inferred role

Driver Families: exported/initcall integration point

Status

integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

• Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.
• Exports symbols or registers init work; inspect boot/module ordering and who consumes the exported contract.
• Touches user memory; correctness depends on fault-safe copying and privilege boundary handling.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/export.h
• linux/fb.h
• linux/module.h
• linux/uaccess.h

Detected Declarations

• function Copyright
• function fb_sys_write
• export fb_sys_read
• export fb_sys_write

Annotated Snippet

#include <linux/export.h>
#include <linux/fb.h>
#include <linux/module.h>
#include <linux/uaccess.h>

ssize_t fb_sys_read(struct fb_info *info, char __user *buf, size_t count,
		    loff_t *ppos)
{
	unsigned long p = *ppos;
	void *src;
	int err = 0;
	unsigned long total_size, c;
	ssize_t ret;

	if (!(info->flags & FBINFO_VIRTFB))
		fb_warn_once(info, "Framebuffer is not in virtual address space.");

	if (!info->screen_buffer)
		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;

	src = info->screen_buffer + p;

	if (info->fbops->fb_sync)
		info->fbops->fb_sync(info);

	c = copy_to_user(buf, src, count);
	if (c)
		err = -EFAULT;
	ret = count - c;

	*ppos += ret;

	return ret ? ret : err;
}
EXPORT_SYMBOL_GPL(fb_sys_read);

ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
		     size_t count, loff_t *ppos)
{
	unsigned long p = *ppos;
	void *dst;
	int err = 0;
	unsigned long total_size, c;
	size_t ret;

	if (!(info->flags & FBINFO_VIRTFB))
		fb_warn_once(info, "Framebuffer is not in virtual address space.");

	if (!info->screen_buffer)
		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;
	}

	dst = info->screen_buffer + p;

	if (info->fbops->fb_sync)
		info->fbops->fb_sync(info);

Annotation

• Immediate include surface: `linux/export.h`, `linux/fb.h`, `linux/module.h`, `linux/uaccess.h`.
• Detected declarations: `function Copyright`, `function fb_sys_write`, `export fb_sys_read`, `export fb_sys_write`.
• Atlas domain: Driver Families / drivers/video.
• Implementation status: integration implementation candidate.
• This snippet crosses the user/kernel memory boundary; validate fault handling and access checks before translating the pattern.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.