Thank you mpi for the response.
I will try to answer to the best of my knowledge.
> Are you sure the name always contain an underscore? Can't it be
> "Button:Button42" ?
It depends. At the moment it is dictated by the default page
/usr/share/misc/usb_hid_usages and the name looks more like "Button:Button
42".
So if someone decides to create another table, he/she could decide to name
it
"Button:Button-42" instead.
However if that would occur other things would break as well, this because
of how the
table is loaded by hid_start().
The patch is made to handle lines defined as " * %99[^\n]". When a line
with spaces
is found, hid_start() will replace the spaces with "_".
> You're passing the string directly to sscanf(3), is that safe?
I was initially uncertain about the safety of sscanf, But when reading the
man-page I could
only identify scenarios using it to scan "%s" as unsafe if you don't supply
a width as this
could lead to buffer overflows.
> Don't you want to parse only unsigned numbers? Or is it possible to
> have "Button:Button_-3" ?
Yes. You are right, which has lead me to replace sscanf with strtonum
instead.
In that way I can do a simple check of input correctness.
To be honest regarding input, I'm not certain about how high values the
hid-specification
allows, it does seem in the cases I have been able to identify, that it is
possible to use
the first two bytes.
Thank you for the questions.
Index: usage.c
===================================================================
RCS file: /cvs/src/lib/libusbhid/usage.c,v
retrieving revision 1.16
diff -u -p -r1.16 usage.c
--- usage.c 8 Oct 2014 04:49:36 -0000 1.16
+++ usage.c 14 Jun 2018 21:56:30 -0000
@@ -265,8 +265,10 @@ int
hid_parse_usage_in_page(const char *name)
{
const char *sep;
+ const char *usage_sep;
unsigned int l;
- int k, j;
+ int k, j, us, parsed_usage;
+ const char *errstr;
sep = strchr(name, ':');
if (sep == NULL)
@@ -278,9 +280,21 @@ hid_parse_usage_in_page(const char *name
return -1;
found:
sep++;
- for (j = 0; j < pages[k].pagesize; j++)
+ for (j = 0; j < pages[k].pagesize; j++) {
+ us = pages[k].page_contents[j].usage;
+ if (us == -1) {
+ usage_sep = strchr(sep, '_');
+ if (usage_sep == NULL)
+ return -1;
+ usage_sep++;
+ parsed_usage = strtonum(usage_sep, 0x1, 0xFFFF,
&errstr);
+ if (errstr == NULL)
+ return (pages[k].usage << 16) |
+ parsed_usage;
+ }
if (strcmp(pages[k].page_contents[j].name, sep) == 0)
return (pages[k].usage << 16) |
pages[k].page_contents[j].usage;
+ }
return -1;
}
2018-06-14 14:54 GMT+02:00 Martin Pieuchot <[email protected]>:
> On 29/05/18(Tue) 22:29, David Bern wrote:
> > Sorry for the spamming.
> > After some research and finding that my fix for issue nr: 2 (
> > hid_usage_in_page() )
> > will break the functionality inside /usr.bin/usbhidaction/usbhidaction.c
> > https://goo.gl/1cWFtR (link to usbhidaction.c)
> >
> > I now change my patch to only include a fix for issue nr: 1
> > More details is described in the previous mail
>
> Are you sure the name always contain an underscore? Can't it be
> "Button:Button42" ?
>
> You're passing the string directly to sscanf(3), is that safe?
>
> Don't you want to parse only unsigned numbers? Or is it possible to
> have "Button:Button_-3" ?
>
> > Index: usage.c
> > ===================================================================
> > RCS file: /cvs/src/lib/libusbhid/usage.c,v
> > retrieving revision 1.16
> > diff -u -p -r1.16 usage.c
> > --- usage.c 8 Oct 2014 04:49:36 -0000 1.16
> > +++ usage.c 29 May 2018 19:45:25 -0000
> > @@ -265,8 +265,9 @@ int
> > hid_parse_usage_in_page(const char *name)
> > {
> > const char *sep;
> > + const char *usage_sep;
> > unsigned int l;
> > - int k, j;
> > + int k, j, us, parsed_usage;
> >
> > sep = strchr(name, ':');
> > if (sep == NULL)
> > @@ -278,9 +279,19 @@ hid_parse_usage_in_page(const char *name
> > return -1;
> > found:
> > sep++;
> > - for (j = 0; j < pages[k].pagesize; j++)
> > + for (j = 0; j < pages[k].pagesize; j++) {
> > + us = pages[k].page_contents[j].usage;
> > + if (us == -1) {
> > + usage_sep = strchr(sep, '_');
> > + if (usage_sep == NULL)
> > + return -1;
> > + if (sscanf(usage_sep, "_%d", &parsed_usage))
> > + return (pages[k].usage << 16) |
> > + parsed_usage;
> > + }
> > if (strcmp(pages[k].page_contents[j].name, sep) == 0)
> > return (pages[k].usage << 16) |
> > pages[k].page_contents[j].usage;
> > + }
> > return -1;
> > }
> >
> >
> > comments? ok?
> >
> > 2018-05-28 13:01 GMT+02:00 David Bern <[email protected]>:
> >
> > > I was suggested off list to give an explanation on what the patch does.
> > >
> > > So please, tell me if I need to clarify more, or make further changes
> to
> > > the code.
> > >
> > > The patch tries to fix two things.
> > > 1. Changes in hid_parse_usage_in_page() fixes problems in parsing
> usages
> > > defined as: * Button %d
> > >
> > > hid_parse_usage_in_page():
> > > Previously - With input "Button:Button_1" returns -1
> > > Now - With input "Button:Button_1" returns 589825
> > >
> > > In the scenario of parsing Button:Button_1 we will not find a usage
> name
> > > matching that string. For example Button:Button_1 is defined as
> > > Button %d in the table.
> > >
> > > We are still able to calculate the proper usage number in the same way
> we
> > > are
> > > able to calculate the proper usage name in hid_usage_in_page().
> > >
> > > The first step is to identify if usage name is shortened. If it is,
> > > usage will hold a value of -1. Then I try to locate a separator char in
> > > the name as "_".
> > > If a separator char is found I use it to read the value as "_%d" to get
> > > the
> > > corresponding usage number
> > >
> > > >+ us = pages[k].page_contents[j].usage;
> > > >+ if (us == -1) {
> > > >+ usage_sep = strchr(sep, '_');
> > > >+ if (usage_sep == NULL)
> > > >+ return -1;
> > > >+ if (sscanf(usage_sep, "_%d", &parsed_usage))
> > > >+ return (pages[k].usage << 16) |
> > > >+ parsed_usage;
> > >
> > >
> > > 2. The text-string that is returned by hid_usage_in_page() misses page
> > > information.
> > > So the changes made in hid_usage_in_page() is to make it the inverse of
> > > hid_parse_usage_in_page()
> > >
> > > In details what the code previously did and now does.
> > >
> > > hid_usage_in_page():
> > > Previously - With input 589825 returns Button_1
> > > Now - With input 589825 returns Button:Button_1
> > >
> > >
> > > The change just adds a pages[k].name to the string, a format that
> > > hid_parse_usage_in_page() expects it to have.
> > > I make formatting in two steps when us == -1 which it is when usage is
> > > shortened
> > > as for example: * Button %d.
> > >
> > > >+ snprintf(fmt, sizeof fmt,
> > > >+ "%%s:%s", pages[k].page_contents[j].name
> );
> > > >+ snprintf(b, sizeof b, fmt, pages[k].name, i);
> > >
> > > The first step is to create a format string that will result in
> something
> > > like
> > > "%s:Button_%d".
> > > The last step I use the fmt-string to create a complete string that
> will
> > > result in
> > > "Button:Button_1"
> > >
> > >
> > >
> > >
> > > 2018-05-24 18:44 GMT+02:00 David Bern <[email protected]>:
> > >
> > >> While I was waiting for comments and feedback I came up with some
> > >> improvements.
> > >> The "logic" is still the same, but the execution is hopefully more
> sane.
> > >>
> > >> Index: usage.c
> > >> ===================================================================
> > >> RCS file: /cvs/src/lib/libusbhid/usage.c,v
> > >> retrieving revision 1.16
> > >> diff -u -p -r1.16 usage.c
> > >> --- usage.c 8 Oct 2014 04:49:36 -0000 1.16
> > >> +++ usage.c 24 May 2018 16:37:54 -0000
> > >> @@ -224,6 +224,7 @@ hid_usage_in_page(unsigned int u)
> > >> {
> > >> int i = HID_USAGE(u), j, k, us;
> > >> int page = HID_PAGE(u);
> > >> + char fmt[100];
> > >> static char b[100];
> > >>
> > >> for (k = 0; k < npages; k++)
> > >> @@ -234,12 +235,16 @@ hid_usage_in_page(unsigned int u)
> > >> for (j = 0; j < pages[k].pagesize; j++) {
> > >> us = pages[k].page_contents[j].usage;
> > >> if (us == -1) {
> > >> - snprintf(b, sizeof b,
> > >> - pages[k].page_contents[j].name, i);
> > >> + snprintf(fmt, sizeof fmt,
> > >> + "%%s:%s", pages[k].page_contents[j].name
> );
> > >> + snprintf(b, sizeof b, fmt, pages[k].name, i);
> > >> + return b;
> > >> + }
> > >> + if (us == i) {
> > >> + snprintf(b, sizeof b, "%s:%s", pages[k].name,
> > >> + pages[k].page_contents[j].name);
> > >> return b;
> > >> }
> > >> - if (us == i)
> > >> - return pages[k].page_contents[j].name;
> > >> }
> > >> bad:
> > >> snprintf(b, sizeof b, "0x%04x", i);
> > >> @@ -265,8 +270,9 @@ int
> > >> hid_parse_usage_in_page(const char *name)
> > >> {
> > >> const char *sep;
> > >> + const char *usage_sep;
> > >> unsigned int l;
> > >> - int k, j;
> > >> + int k, j, us, parsed_usage;
> > >>
> > >> sep = strchr(name, ':');
> > >> if (sep == NULL)
> > >> @@ -278,9 +284,19 @@ hid_parse_usage_in_page(const char *name
> > >> return -1;
> > >> found:
> > >> sep++;
> > >> - for (j = 0; j < pages[k].pagesize; j++)
> > >> + for (j = 0; j < pages[k].pagesize; j++) {
> > >> + us = pages[k].page_contents[j].usage;
> > >> + if (us == -1) {
> > >> + usage_sep = strchr(sep, '_');
> > >> + if (usage_sep == NULL)
> > >> + return -1;
> > >> + if (sscanf(usage_sep, "_%d", &parsed_usage))
> > >> + return (pages[k].usage << 16) |
> > >> + parsed_usage;
> > >> + }
> > >> if (strcmp(pages[k].page_contents[j].name, sep) == 0)
> > >> return (pages[k].usage << 16) |
> > >> pages[k].page_contents[j].usage;
> > >> + }
> > >> return -1;
> > >> }
> > >>
> > >>
> > >>
> > >> 2018-05-21 23:12 GMT+02:00 David Bern <[email protected]>:
> > >>
> > >>> First diff "solves" point 1 & 2. Second diff is on the parts of the
> > >>> manual that does not match the usbhid.h
> > >>>
> > >>> Index: usage.c
> > >>> ===================================================================
> > >>> RCS file: /cvs/src/lib/libusbhid/usage.c,v
> > >>> retrieving revision 1.16
> > >>> diff -u -p -r1.16 usage.c
> > >>> --- usage.c 8 Oct 2014 04:49:36 -0000 1.16
> > >>> +++ usage.c 21 May 2018 21:06:24 -0000
> > >>> @@ -224,6 +224,7 @@ hid_usage_in_page(unsigned int u)
> > >>> {
> > >>> int i = HID_USAGE(u), j, k, us;
> > >>> int page = HID_PAGE(u);
> > >>> + char usage_name[100];
> > >>> static char b[100];
> > >>>
> > >>> for (k = 0; k < npages; k++)
> > >>> @@ -234,12 +235,18 @@ hid_usage_in_page(unsigned int u)
> > >>> for (j = 0; j < pages[k].pagesize; j++) {
> > >>> us = pages[k].page_contents[j].usage;
> > >>> if (us == -1) {
> > >>> - snprintf(b, sizeof b,
> > >>> + snprintf(usage_name, sizeof usage_name,
> > >>> pages[k].page_contents[j].name, i);
> > >>> + snprintf(b, sizeof b,
> > >>> + "%s:%s", pages[k].name, usage_name);
> > >>> + return b;
> > >>> + }
> > >>> + if (us == i) {
> > >>> + snprintf(b, sizeof b,
> > >>> + "%s:%s", pages[k].name,
> > >>> + pages[k].page_contents[j].name);
> > >>> return b;
> > >>> }
> > >>> - if (us == i)
> > >>> - return pages[k].page_contents[j].name;
> > >>> }
> > >>> bad:
> > >>> snprintf(b, sizeof b, "0x%04x", i);
> > >>> @@ -265,8 +272,9 @@ int
> > >>> hid_parse_usage_in_page(const char *name)
> > >>> {
> > >>> const char *sep;
> > >>> + const char *usage_sep;
> > >>> unsigned int l;
> > >>> - int k, j;
> > >>> + int k, j, us, parsed_usage;
> > >>>
> > >>> sep = strchr(name, ':');
> > >>> if (sep == NULL)
> > >>> @@ -277,10 +285,20 @@ hid_parse_usage_in_page(const char *name
> > >>> goto found;
> > >>> return -1;
> > >>> found:
> > >>> + usage_sep = strchr(sep, '_');
> > >>> sep++;
> > >>> - for (j = 0; j < pages[k].pagesize; j++)
> > >>> + for (j = 0; j < pages[k].pagesize; j++) {
> > >>> + us = pages[k].page_contents[j].usage;
> > >>> + if (us == -1) {
> > >>> + if (usage_sep == NULL)
> > >>> + return -1;
> > >>> + if (sscanf(usage_sep, "_%d", &parsed_usage))
> > >>> + return (pages[k].usage << 16 |
> > >>> + parsed_usage);
> > >>> + }
> > >>> if (strcmp(pages[k].page_contents[j].name, sep) ==
> 0)
> > >>> return (pages[k].usage << 16) |
> > >>> pages[k].page_contents[j].usage;
> > >>> + }
> > >>> return -1;
> > >>> }
> > >>>
> > >>> Index: usbhid.3
> > >>> ===================================================================
> > >>> RCS file: /cvs/src/lib/libusbhid/usbhid.3,v
> > >>> retrieving revision 1.17
> > >>> diff -u -p -r1.17 usbhid.3
> > >>> --- usbhid.3 13 May 2014 14:05:02 -0000 1.17
> > >>> +++ usbhid.3 21 May 2018 21:02:21 -0000
> > >>> @@ -65,22 +65,22 @@
> > >>> .Fn hid_report_size "report_desc_t d" "hid_kind_t k" "int id"
> > >>> .Ft int
> > >>> .Fn hid_locate "report_desc_t d" "u_int usage" "hid_kind_t k"
> > >>> "hid_item_t *h" "int id"
> > >>> -.Ft char *
> > >>> +.Ft const char *
> > >>> .Fn hid_usage_page "int i"
> > >>> -.Ft char *
> > >>> +.Ft const char *
> > >>> .Fn hid_usage_in_page "u_int u"
> > >>> .Ft int
> > >>> .Fn hid_parse_usage_page "const char *"
> > >>> -.Ft char *
> > >>> +.Ft int
> > >>> .Fn hid_parse_usage_in_page "const char *"
> > >>> .Ft void
> > >>> .Fn hid_init "char *file"
> > >>> .Ft int
> > >>> .Fn hid_start "char *file"
> > >>> -.Ft int
> > >>> +.Ft int32_t
> > >>> .Fn hid_get_data "void *data" "hid_item_t *h"
> > >>> .Ft void
> > >>> -.Fn hid_set_data "void *data" "hid_item_t *h" "u_int data"
> > >>> +.Fn hid_set_data "void *data" "hid_item_t *h" "int32_t data"
> > >>> .Sh DESCRIPTION
> > >>> The
> > >>> .Nm
> > >>>
> > >>>
> > >>>
> > >>> 2018-05-21 12:07 GMT+02:00 Martin Pieuchot <[email protected]>:
> > >>>
> > >>>> On 18/05/18(Fri) 10:01, David Bern wrote:
> > >>>> > Hello!
> > >>>> >
> > >>>> > Have been using libusbhid and discovered a couple of
> discrepancies in
> > >>>> > the man-page (libusbhid.3) and the source of usage.c
> > >>>> >
> > >>>> > Some are just factual misses, but I also got (what I think is) 2
> > >>>> errors.
> > >>>> > I will try to explain them;
> > >>>> >
> > >>>> > 1. (This is the I think is an error but not sure). The man-page
> tells
> > >>>> me
> > >>>> > that hid_usage_in_page and hid_parse_usage_in_page are each
> > >>>> > others inverse.
> > >>>> > If I haven't misunderstood the practical meaning of inverse in
> this
> > >>>> > case then this should be true:
> > >>>> > x == hid_parse_usage_in_page(hid_usage_in_page(x)).
> > >>>> >
> > >>>> > My observation:
> > >>>> > The main reason to why this isnt true, is that hid_usage_in_page()
> > >>>> > returns the data of pages[k].page_contents[j].name
> > >>>> > while hid_parse_usage_in_page() expects the data to
> > >>>> > contain "%s:%s", pages[k].name, pages[k].page_contents[j].name
> > >>>> >
> > >>>> > The reason I ask instead of just posting working code is this:
> > >>>> > Am I misunderstanding the manual? In that case, the solution I
> want
> > >>>> > to send in is a change in that sentence
> > >>>> > Or Is the manual correct and the behavior of hid_usage_in_page()
> > >>>> wrong,
> > >>>> > is this something I can correct without breaking other systems?
> > >>>> >
> > >>>> >
> > >>>> > 2. The second error I found is located in
> hid_parse_usage_in_page().
> > >>>> > It is unable to parse values found in page Button.
> > >>>> >
> > >>>> > My observation:
> > >>>> > usage.c is using a standard table named usb_hid_pages. In that
> table
> > >>>> > we got a page called Buttons.
> > >>>> > the usages in that page is shortened to "* Button %d".
> > >>>> > I believe this is the cause of why hid_parse_usage_in_page() is
> > >>>> getting
> > >>>> > the pagesize "wrong" and therefor unable to parse any button in
> the
> > >>>> > button page. I guess this is the case with other similar cases as
> > >>>> well.
> > >>>> >
> > >>>> > my conclusion is that it would be possible to handle similar
> cases in
> > >>>> a
> > >>>> > similar way as it is handled in hid_usage_in_page().
> > >>>> >
> > >>>> >
> > >>>> > As this is my first "issue" I would love to get as much feedback
> as
> > >>>> > possible so I can work on delivering a desirable and usable patch
> in
> > >>>> > my first try.
> > >>>>
> > >>>> Just send a diff, then we'll look at it 8)
> > >>>>
> > >>>
> > >>>
> > >>
> > >
>
