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ibmpc: Revert 2a0471fd on ibmpc_host_send()

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Restoring old recv_data can overwrite response data when the response is
multi-byte. This can happen when device responds with multiple bytes quickly,
for example Logitech MX518(PS/2) sends FA 00 in short period to F2 command
while most of devices doesn't send second byte that fast.

recv_data is cleared when calling ibmpc_host_send() you will have to
retain the data yourself before calling it. Or you have to make sure
that recv_data is empty as possible before calling the function.

Alternatively, ibmpc_host_send() can be changed to check if recv_data is
empty before seding command.
This commit is contained in:
tmk 2021-06-19 18:18:51 +09:00
parent 4ed3e40fc0
commit 22b6e87f37
1 changed files with 1 additions and 8 deletions
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9
tmk_core/protocol/ibmpc.c
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@ -153,19 +153,12 @@ RETRY:
WAIT(data_hi, 300, 7);
WAIT(clock_hi, 300, 8);
uint16_t d = recv_data;
// clear buffer to get response correctly
ibmpc_host_isr_clear();
idle();
IBMPC_INT_ON();
int16_t r = ibmpc_host_recv_response();
if (d != 0xFFFF) dprintf("r:%04X ", d);
ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
recv_data = d;
}
return r;
return ibmpc_host_recv_response();
ERROR:
// Retry for Z-150 AT start bit error
if (ibmpc_error == 1 && retry++ < 10) {