Re: [PATCH 1/2] HID: core: Provide new max_buffer_size attribute to over-ride the default

[Lee Jones <lee@kernel.org>]

On Wed, 18 Jan 2023, Jiri Kosina wrote:

> On Fri, 13 Jan 2023, Lee Jones wrote:
> 
> > Presently, when a report is processed, its size is compared solely 
> > against the value specified by user-space.  
> 
> While I am generally fine with the idea, I don't understand this sentence. 
> What exactly do you mean by 'specified by user-space'? It's defined as a 
> compile-time constant.
> 
> > If the received report ends up being smaller than this, the
> > remainder of the buffer is zeroed. 

Apologies for any ambiguity.

"its size" == "compile-time constant"

Would "its maximum size" read better?

These sentences are an attempt to describe this statement:

    if (csize < rsize) {
        dbg_hid("report %d is too short, (%d < %d)\n", report->id,
            csize, rsize);
        memset(cdata + csize, 0, rsize - csize);
    }

Where csize is "the [size of the] received report" and rsize is the
"value [size] specified by user-space".  Thus, if user-space says the
report will be 8-Bytes (rsize) and it actually only only submits 6-Bytes
(csize), then the subsystem will complain that the "report is too short"
and it will attempt to zero the seemingly unused 2-Bytes.

-- 
Lee Jones [李琼斯]