drivers/nvmem/rmem.c

Source file repositories/reference/linux-study-clean/drivers/nvmem/rmem.c

File Facts

System
Linux kernel
Corpus path
drivers/nvmem/rmem.c
Extension
.c
Size
4367 bytes
Lines
179
Domain
Driver Families
Bucket
drivers/nvmem
Inferred role
Driver Families: implementation source
Status
source 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.

Dependency Surface

Detected Declarations

Annotated Snippet

struct rmem {
	struct device *dev;
	struct nvmem_device *nvmem;
	struct reserved_mem *mem;
};

struct rmem_match_data {
	int (*checksum)(struct rmem *priv);
};

struct __packed rmem_eyeq5_header {
	u32 magic;
	u32 version;
	u32 size;
};

#define RMEM_EYEQ5_MAGIC	((u32)0xDABBAD00)

static int rmem_read(void *context, unsigned int offset,
		     void *val, size_t bytes)
{
	struct rmem *priv = context;
	void *addr;

	if ((phys_addr_t)offset + bytes > priv->mem->size)
		return -EIO;

	/*
	 * Only map the reserved memory at this point to avoid potential rogue
	 * kernel threads inadvertently modifying it. Based on the current
	 * uses-cases for this driver, the performance hit isn't a concern.
	 * Nor is likely to be, given the nature of the subsystem. Most nvmem
	 * devices operate over slow buses to begin with.
	 *
	 * An alternative would be setting the memory as RO, set_memory_ro(),
	 * but as of Dec 2020 this isn't possible on arm64.
	 */
	addr = memremap(priv->mem->base, priv->mem->size, MEMREMAP_WB);
	if (!addr) {
		dev_err(priv->dev, "Failed to remap memory region\n");
		return -ENOMEM;
	}

	memcpy(val, addr + offset, bytes);

	memunmap(addr);

	return 0;
}

static int rmem_eyeq5_checksum(struct rmem *priv)
{
	void *buf __free(kfree) = NULL;
	struct rmem_eyeq5_header header;
	u32 computed_crc, *target_crc;
	size_t data_size;
	int ret;

	ret = rmem_read(priv, 0, &header, sizeof(header));
	if (ret)
		return ret;

	if (header.magic != RMEM_EYEQ5_MAGIC)
		return -EINVAL;

	/*
	 * Avoid massive kmalloc() if header read is invalid;
	 * the check would be done by the next rmem_read() anyway.
	 */
	if (header.size > priv->mem->size)
		return -EINVAL;

	/*
	 *           0 +-------------------+
	 *             | Header (12 bytes) | \
	 *             +-------------------+ |
	 *             |                   | | data to be CRCed
	 *             |        ...        | |
	 *             |                   | /
	 *   data_size +-------------------+
	 *             |   CRC (4 bytes)   |
	 * header.size +-------------------+
	 */

	buf = kmalloc(header.size, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	ret = rmem_read(priv, 0, buf, header.size);
	if (ret)

Annotation

Implementation Notes