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| author | Todd Broch <tbroch@chromium.org> | 2015-05-20 16:05:10 -0700 |
|---|---|---|
| committer | ChromeOS Commit Bot <chromeos-commit-bot@chromium.org> | 2015-05-22 21:27:33 +0000 |
| commit | 1a996dc19c82f9241226c8e6ff5f168d2c2c7ebc (patch) | |
| tree | f6259f167b731a1c5904dbf9d2cc102ab4734b75 /driver/mcdp28x0.c | |
| parent | 37a23855f7bba522f4cb300d8f4547764e5e3578 (diff) | |
| download | chrome-ec-1a996dc19c82f9241226c8e6ff5f168d2c2c7ebc.tar.gz | |
mcdp28x0: Add checksum verification to rx_serial.
Signed-off-by: Todd Broch <tbroch@chromium.org>
BRANCH=samus
BUG=chrome-os-partner:35939
TEST=compiles, MCDP_READY gpio still asserted.
Change-Id: If20a695380dc44d899951faeaa805bf7acfae1e1
Reviewed-on: https://chromium-review.googlesource.com/272691
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Commit-Queue: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
Diffstat (limited to 'driver/mcdp28x0.c')
| -rw-r--r-- | driver/mcdp28x0.c | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/driver/mcdp28x0.c b/driver/mcdp28x0.c index 7fba0bd035..a3a2043619 100644 --- a/driver/mcdp28x0.c +++ b/driver/mcdp28x0.c @@ -50,15 +50,15 @@ USART_CONFIG(usart_mcdp, CONFIG_MCDP28X0, 115200, rx_queue, tx_queue, /** * Compute checksum. * + * @seed initial value of checksum. * @msg message bytes to compute checksum on. * @cnt count of message bytes. * @return partial checksum. */ -static uint8_t compute_checksum(const uint8_t *msg, int cnt) +static uint8_t compute_checksum(uint8_t seed, const uint8_t *msg, int cnt) { int i; - /* 1st byte (not in msg) is always cnt + 2, so seed chksum with that */ - uint8_t chksum = cnt + 2; + uint8_t chksum = seed; for (i = 0; i < cnt; i++) chksum += msg[i]; @@ -69,8 +69,8 @@ static uint8_t compute_checksum(const uint8_t *msg, int cnt) * transmit message over serial * * Packet consists of: - * msg[0] == length including this byte + cnt + chksum - * msg[1] == 1st message byte + * msg[0] == length of entire packet + * msg[1] == 1st message byte (typically command) * msg[cnt+1] == last message byte * msg[cnt+2] == checksum * @@ -81,7 +81,8 @@ static uint8_t compute_checksum(const uint8_t *msg, int cnt) static int tx_serial(const uint8_t *msg, int cnt) { uint8_t out = cnt + 2; - uint8_t chksum = compute_checksum(msg, cnt); + /* 1st byte (not in msg) is always cnt + 2, so seed chksum with that */ + uint8_t chksum = compute_checksum(cnt + 2, msg, cnt); if (out_stream_write(&usart_out.out, &out, 1) != 1) return EC_ERROR_UNKNOWN; @@ -100,6 +101,15 @@ static int tx_serial(const uint8_t *msg, int cnt) /** * receive message over serial * + * While definitive documentation is lacking its believed the following receive + * packet is always true. + * + * Packet consists of: + * msg[0] == length of entire packet + * msg[1] == 1st message byte (typically command) + * msg[cnt+2] == last message byte + * msg[cnt+3] == checksum + * * @msg pointer to buffer to read message into * @cnt count of message bytes * @return zero if success, error code otherwise @@ -119,6 +129,9 @@ static int rx_serial(uint8_t *msg, int cnt) print_buffer(msg, cnt); + if (msg[cnt-1] != compute_checksum(0, msg, cnt-1)) + return EC_ERROR_UNKNOWN; + return !(read == cnt); } @@ -143,11 +156,6 @@ int mcdp_get_info(struct mcdp_info *info) if (rx_serial(inbuf, sizeof(inbuf))) return EC_ERROR_UNKNOWN; - /* check length & returned command ... no checksum provided */ - if (((inbuf[0] - 1) != sizeof(inbuf)) || - (inbuf[1] != MCDP_CMD_GETINFO)) - return EC_ERROR_UNKNOWN; - memcpy(info, &inbuf[2], MCDP_LEN_GETINFO); #ifdef MCDP_DEBUG |