Hi Greg,
On 27-07-2025 20:16, Usyskin, Alexander wrote:
Subject: Re: [PATCH 2/9] mei: late_bind: add late binding component driver
On Wed, Jul 16, 2025 at 02:26:26PM +0000, Usyskin, Alexander wrote:
+ if (bytes < sizeof(rsp)) {
+ dev_err(dev, "bad response from the firmware: size
%zd <
%zu\n",
+ bytes, sizeof(rsp));
+ ret = -EPROTO;
+ goto end;
+ }
Why not check this above when you check against the size of the
header?
You only need one size check, not 2.
Firmware may return only header with result field set without the data.
Then the firmware is broken :)
We are parsing the header first and then starting to parse data.
If we check for whole message size at the beginning we'll miss the result
data.
You mean you will make it harder to debug the firmware, as you will not
be printing out the header information? Or something else? The
bytes variable HAS to match the full structure size, not just the header
size, according to this code. So just test for that and be done with
it!
The CSME firmware returns only command header if, like, command is not
recognised.
This may happen because of firmware bug or for firmware is
configured/compiled
that way.
This seems reasonable for the complex protocols where firmware may not be
aware of this particular command at all and have no idea what the data size
it
should send in reply.
Printing result from the header will allow us to understand either this is the
firmware
problem or driver sent something wrong.
Then make it obvious in your checking and in your error messages as to
what you are doing here. Checking the size of the buffer in two
different places, with different values is very odd, and deserves a lot
of explaination.
Is this addition
/*
* Received message size may be smaller than the full message size when
* reply contains only MKHI header with result field set to the error
code.
* Check the header size and content first to output exact error, if
needed,
* and then process to the whole message.
*/
and remodelling error messages like "received less then header size from the
firmware"
made it clean for people not involved with our firmware?
I'm too deep in this to judge the wording.
I'm planning to include the following code in the next revision. Does
this change align with your recommendation?
+ /*
+ * Received message size may be smaller than the full
message size when
+ * reply contains only MKHI header with result field set to
the error code.
+ * Check the header size and content first to output exact
error, if needed,
+ * and then process to the whole message.
+ */
if (bytes < sizeof(rsp.header)) {
- dev_err(dev, "bad response header from the firmware:
size %zd < %zu\n",
+ dev_err(dev, "received less than header size from
the firmware: %zd < %zu\n",
bytes, sizeof(rsp.header));
ret = -EPROTO;
goto end;
}
if (mei_lb_check_response(dev, &rsp.header)) {
- dev_err(dev, "bad result response from the firmware:
0x%x\n",
+ dev_err(dev, "bad response from the firmware:
header: 0x%x\n",
*(uint32_t *)&rsp.header);
ret = -EPROTO;
goto end;
}
if (bytes < sizeof(rsp)) {
- dev_err(dev, "bad response from the firmware: size
%zd < %zu\n",
+ dev_err(dev, "received less than message size from
the firmware: %zd < %zu\n",
bytes, sizeof(rsp));
ret = -EPROTO;
goto end;
Thanks,
Badal
- -
Thanks,
Sasha
