[flashrom] [PATCH] SFDP: Fetch parameter table in a more portable way

[Carl-Daniel Hailfinger]

SFDP parameter table reads expect a dummy byte between written and read
data on the SPI bus. Read that dummy byte instead of writing it to be
compatible with more (all) programmer drivers.
Reduce SFDP parameter table read chunk size from 8 to 2 to handle
programmers with small readcount limits.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>

Index: flashrom-sfdp_read_dummy_reduce_param_chunksize/sfdp.c
===================================================================
--- flashrom-sfdp_read_dummy_reduce_param_chunksize/sfdp.c	(Revision 1505)
+++ flashrom-sfdp_read_dummy_reduce_param_chunksize/sfdp.c	(Arbeitskopie)
@@ -19,6 +19,7 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <string.h>
 #include "flash.h"
 #include "spi.h"
 #include "chipdrivers.h"
@@ -26,31 +27,39 @@
 static int spi_sfdp_read_sfdp_chunk(struct flashctx *flash, uint32_t address, uint8_t *buf, int len)
 {
 	int i, ret;
+	uint8_t *newbuf;
 	const unsigned char cmd[JEDEC_SFDP_OUTSIZE] = {
 		JEDEC_SFDP,
 		(address >> 16) & 0xff,
 		(address >> 8) & 0xff,
 		(address >> 0) & 0xff,
 		/* FIXME: the following dummy byte explodes on some programmers.
-		 * One possible workaround would be to read the dummy byte
+		 * One workaround is to read the dummy byte
 		 * instead and discard its value.
 		 */
 		0
 	};
 	msg_cspew("%s: addr=0x%x, len=%d, data:\n", __func__, address, len);
-	ret = spi_send_command(flash, sizeof(cmd), len, cmd, buf);
+	newbuf = malloc(len + 1);
+	if (!newbuf)
+		return SPI_PROGRAMMER_ERROR;
+	ret = spi_send_command(flash, sizeof(cmd) - 1, len + 1, cmd, newbuf);
+	memmove(buf, newbuf + 1, len);
+	free(newbuf);
+	if (ret)
+		return ret;
 	for (i = 0; i < len; i++)
 		msg_cspew(" 0x%02x", buf[i]);
 	msg_cspew("\n");
-	return ret;
+	return 0;
 }
 
 static int spi_sfdp_read_sfdp(struct flashctx *flash, uint32_t address, uint8_t *buf, int len)
 {
-	/* FIXME: this is wrong. There are different upper bounds for the number
-	 * of bytes to read on the various programmers (even depending on the
-	 * rest of the structure of the transaction).*/
-	int maxstep = 8;
+	/* FIXME: There are different upper bounds for the number of bytes to
+	 * read on the various programmers (even depending on the rest of the
+	 * structure of the transaction). 2 is a safe bet. */
+	int maxstep = 2;
 	int ret = 0;
 	while (len > 0) {
 		int step = min(len, maxstep);


-- 
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