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[PATCH v2] hw/nvram: at24 return 0xff if 1 byte address
From: |
Patrick Venture |
Subject: |
[PATCH v2] hw/nvram: at24 return 0xff if 1 byte address |
Date: |
Mon, 20 Dec 2021 13:21:37 -0800 |
The at24 eeproms are 2 byte devices that return 0xff when they are read
from with a partial (1-byte) address written. This distinction was
found comparing model behavior to real hardware testing.
Tested: `i2ctransfer -f -y 45 w1@85 0 r1` returns 0xff instead of next
byte
Signed-off-by: Patrick Venture <venture@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: Reordered the event switch to remove explicit branch and use fallthrough.
---
hw/nvram/eeprom_at24c.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/hw/nvram/eeprom_at24c.c b/hw/nvram/eeprom_at24c.c
index af6f5dbb99..b956b8e2b2 100644
--- a/hw/nvram/eeprom_at24c.c
+++ b/hw/nvram/eeprom_at24c.c
@@ -58,9 +58,10 @@ int at24c_eeprom_event(I2CSlave *s, enum i2c_event event)
switch (event) {
case I2C_START_SEND:
- case I2C_START_RECV:
case I2C_FINISH:
ee->haveaddr = 0;
+ /* fallthrough */
+ case I2C_START_RECV:
DPRINTK("clear\n");
if (ee->blk && ee->changed) {
int len = blk_pwrite(ee->blk, 0, ee->mem, ee->rsize, 0);
@@ -84,6 +85,10 @@ uint8_t at24c_eeprom_recv(I2CSlave *s)
EEPROMState *ee = AT24C_EE(s);
uint8_t ret;
+ if (ee->haveaddr == 1) {
+ return 0xff;
+ }
+
ret = ee->mem[ee->cur];
ee->cur = (ee->cur + 1u) % ee->rsize;
--
2.34.1.307.g9b7440fafd-goog
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