Re: [PATCH 2/8] usb: gadget: add anonymous definition in some struct for trace purpose

[Alan Stern <stern@rowland.harvard.edu>]

On Fri, Sep 15, 2023 at 09:02:48AM +0800, Linyu Yuan wrote:
> 
> On 9/14/2023 10:54 PM, Alan Stern wrote:
> > You didn't include the version number in the Subject: line.  Undoubtedly
> > Greg's automatic error checker will warn you about this.  Unless the
> > version number is clearly marked for each patch, it's difficult for his
> > programs to tell which email message contains the most recent version.
> > 
> > On Thu, Sep 14, 2023 at 06:02:56PM +0800, Linyu Yuan wrote:
> > > Some UDC trace event will save usb udc information, but it use one int
> > > size buffer to save one bit information of usb udc, it is wast trace
> > > buffer.
> > > 
> > > Add anonymous union which have one u32 member can be used by trace event
> > > during fast assign stage to save more entries with same trace ring buffer
> > > size.
> > > 
> > > Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
> > > ---
> > And you didn't include the version change information here, below the
> > "---" line.
> > 
> > Apart from that, this is a _lot_ better than before!  I don't know if
> > Greg will think this change is worth merging, but at least now it's
> > possible to read the code and understand what's going on.
> 
> 
> according Steven's comment, maybe will always save data in little endian at
> trace event
> 
> fast assign stage.
> 
> it will add definition of bit field back.

Yes, that would be even better because you wouldn't have to change the 
definition of struct usb_gadget or struct usb_endpoint at all.  The fast 
assign stage can simply do:

	__entry->dw1 = (g->sg_supported << 0) |
			(g->is_otg << 1) |
			...

and then you can easily access the individual bits in __entry.  It 
wouldn't be as fast but it would still save a lot of space.

Alan Stern