drivers/net/dsa/sja1105/sja1105_spi.c

Source file repositories/reference/linux-study-clean/drivers/net/dsa/sja1105/sja1105_spi.c

File Facts

System
Linux kernel
Corpus path
drivers/net/dsa/sja1105/sja1105_spi.c
Extension
.c
Size
33378 bytes
Lines
978
Domain
Driver Families
Bucket
drivers/net
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 sja1105_chunk {
	u8	*buf;
	size_t	len;
	u64	reg_addr;
};

static void
sja1105_spi_message_pack(void *buf, const struct sja1105_spi_message *msg)
{
	const int size = SJA1105_SIZE_SPI_MSG_HEADER;

	memset(buf, 0, size);

	sja1105_pack(buf, &msg->access,     31, 31, size);
	sja1105_pack(buf, &msg->read_count, 30, 25, size);
	sja1105_pack(buf, &msg->address,    24,  4, size);
}

/* If @rw is:
 * - SPI_WRITE: creates and sends an SPI write message at absolute
 *		address reg_addr, taking @len bytes from *buf
 * - SPI_READ:  creates and sends an SPI read message from absolute
 *		address reg_addr, writing @len bytes into *buf
 */
static int sja1105_xfer(const struct sja1105_private *priv,
			sja1105_spi_rw_mode_t rw, u64 reg_addr, u8 *buf,
			size_t len, struct ptp_system_timestamp *ptp_sts)
{
	u8 hdr_buf[SJA1105_SIZE_SPI_MSG_HEADER] = {0};
	struct spi_device *spi = priv->spidev;
	struct spi_transfer xfers[2] = {0};
	struct spi_transfer *chunk_xfer;
	struct spi_transfer *hdr_xfer;
	struct sja1105_chunk chunk;
	int num_chunks;
	int rc, i = 0;

	num_chunks = DIV_ROUND_UP(len, priv->max_xfer_len);

	chunk.reg_addr = reg_addr;
	chunk.buf = buf;
	chunk.len = min_t(size_t, len, priv->max_xfer_len);

	hdr_xfer = &xfers[0];
	chunk_xfer = &xfers[1];

	for (i = 0; i < num_chunks; i++) {
		struct spi_transfer *ptp_sts_xfer;
		struct sja1105_spi_message msg;

		/* Populate the transfer's header buffer */
		msg.address = chunk.reg_addr;
		msg.access = rw;
		if (rw == SPI_READ)
			msg.read_count = chunk.len / 4;
		else
			/* Ignored */
			msg.read_count = 0;
		sja1105_spi_message_pack(hdr_buf, &msg);
		hdr_xfer->tx_buf = hdr_buf;
		hdr_xfer->len = SJA1105_SIZE_SPI_MSG_HEADER;

		/* Populate the transfer's data buffer */
		if (rw == SPI_READ)
			chunk_xfer->rx_buf = chunk.buf;
		else
			chunk_xfer->tx_buf = chunk.buf;
		chunk_xfer->len = chunk.len;

		/* Request timestamping for the transfer. Instead of letting
		 * callers specify which byte they want to timestamp, we can
		 * make certain assumptions:
		 * - A read operation will request a software timestamp when
		 *   what's being read is the PTP time. That is snapshotted by
		 *   the switch hardware at the end of the command portion
		 *   (hdr_xfer).
		 * - A write operation will request a software timestamp on
		 *   actions that modify the PTP time. Taking clock stepping as
		 *   an example, the switch writes the PTP time at the end of
		 *   the data portion (chunk_xfer).
		 */
		if (rw == SPI_READ)
			ptp_sts_xfer = hdr_xfer;
		else
			ptp_sts_xfer = chunk_xfer;
		ptp_sts_xfer->ptp_sts_word_pre = ptp_sts_xfer->len - 1;
		ptp_sts_xfer->ptp_sts_word_post = ptp_sts_xfer->len - 1;
		ptp_sts_xfer->ptp_sts = ptp_sts;

		/* Calculate next chunk */

Annotation

Implementation Notes