Re: [PATCH v6] usb: core: Add "quirks" parameter for usbcore

[Kai Heng Feng]

Kai Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> wrote:

> Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> > On Tue, Mar 13, 2018 at 03:26:19PM +0800, Kai-Heng Feng wrote:
> > > +	usbcore.quirks=
> > > +			[USB] A list of quirks entries to supplement or
> > > +			override the built-in usb core quirk list.  List
> > > +			entries are separated by commas.  Each entry has
> > > +			the form VID:PID:Flags where VID and PID are Vendor
> > > +			and Product ID values (4-digit hex numbers) and
> > > +			Flags is a set of characters, each corresponding
> > > +			to a common usb core quirk flag as follows:
> >
> > This doesn't really tell me that the specified quirks will be XORed with
> > the built-in quirks.  Maybe something like ...
> >
> > 			[USB] A list of quirk entries to augment the
> > 			built-in usb core quirk list.  List entries are
> > 			separated by commas.  Each entry has the form
> > 			VendorID:ProductID:Flags.  The IDs are 4-digit hex
> > 			numbers and Flags is a set of letters.  Each letter
> > 			will change the built-in quirk; setting it if it is
> > 			clear and clearing it if it is set.  The letters
> > 			have the following meanings:
>
> Thanks, will update the description to specify the XOR behavior.
>
> > > +		/* Each entry consists of VID:PID:flags */
> > > +		field = strsep(&p, ":");
> > > +		if (!field)
> > > +			break;
> > > +
> > > +		if (kstrtou16(field, 16, &vid))
> > > +			break;
> > > +
> > > +		field = strsep(&p, ":");
> > > +		if (!field)
> > > +			break;
> > > +
> > > +		if (kstrtou16(field, 16, &pid))
> > > +			break;
> >
> > Is there a reason to not use sscanf here like hid-quirks.c does?
>
> Actually I use sscanf in previous patch version. Using kstrto* isn't  
> needed anymore, I'll use sscanf in next version.

Okay, I remember why I don't use sscanf, mainly because the quirk_param in  
hid-quirks.c is charp instead of char, so using sscanf is trivia for it.

We use plain char* here because of module_param_cb(), so I guess using  
sscanf doesn't make much sense here. strsep() isn't the most elegant  
solution but it does its job well.

I'll update the description and send a new patch.

Kai-Heng

> Kai-Heng