* [bug report] usb: host: Faraday fotg210-hcd driver
@ 2020-02-11 15:03 Dan Carpenter
2020-02-11 15:24 ` Alan Stern
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2020-02-11 15:03 UTC (permalink / raw)
To: linux-usb; +Cc: john453
Hello USB devs,
The patch 7d50195f6c50: "usb: host: Faraday fotg210-hcd driver" from
Jul 29, 2013, leads to the following static checker warning:
drivers/usb/host/fotg210-hcd.c:3945 iso_stream_init()
warn: mask and shift to zero
drivers/usb/host/fotg210-hcd.c
3922 static void iso_stream_init(struct fotg210_hcd *fotg210,
3923 struct fotg210_iso_stream *stream, struct usb_device *dev,
3924 int pipe, unsigned interval)
3925 {
3926 u32 buf1;
3927 unsigned epnum, maxp;
3928 int is_input;
3929 long bandwidth;
3930 unsigned multi;
3931
3932 /*
3933 * this might be a "high bandwidth" highspeed endpoint,
3934 * as encoded in the ep descriptor's wMaxPacket field
3935 */
3936 epnum = usb_pipeendpoint(pipe);
3937 is_input = usb_pipein(pipe) ? USB_DIR_IN : 0;
3938 maxp = usb_maxpacket(dev, pipe, !is_input);
3939 if (is_input)
3940 buf1 = (1 << 11);
3941 else
3942 buf1 = 0;
3943
3944 maxp = max_packet(maxp);
3945 multi = hb_mult(maxp);
3946 buf1 |= maxp;
3947 maxp *= multi;
3948
3949 stream->buf0 = cpu_to_hc32(fotg210, (epnum << 8) | dev->devnum);
3950 stream->buf1 = cpu_to_hc32(fotg210, buf1);
3951 stream->buf2 = cpu_to_hc32(fotg210, multi);
The problem is these two defines:
#define max_packet(wMaxPacketSize) ((wMaxPacketSize) & 0x07ff)
#define hb_mult(wMaxPacketSize) (1 + (((wMaxPacketSize) >> 11) & 0x03))
0x07ff >> 11 is always zero so multi is always 1.
Should we pass the original value that usb_maxpacket() returned instead
of the masked value?
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [bug report] usb: host: Faraday fotg210-hcd driver
2020-02-11 15:03 [bug report] usb: host: Faraday fotg210-hcd driver Dan Carpenter
@ 2020-02-11 15:24 ` Alan Stern
2020-02-11 15:47 ` Alan Stern
0 siblings, 1 reply; 3+ messages in thread
From: Alan Stern @ 2020-02-11 15:24 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-usb, john453
On Tue, 11 Feb 2020, Dan Carpenter wrote:
> Hello USB devs,
>
> The patch 7d50195f6c50: "usb: host: Faraday fotg210-hcd driver" from
> Jul 29, 2013, leads to the following static checker warning:
>
> drivers/usb/host/fotg210-hcd.c:3945 iso_stream_init()
> warn: mask and shift to zero
>
> drivers/usb/host/fotg210-hcd.c
> 3922 static void iso_stream_init(struct fotg210_hcd *fotg210,
> 3923 struct fotg210_iso_stream *stream, struct usb_device *dev,
> 3924 int pipe, unsigned interval)
> 3925 {
> 3926 u32 buf1;
> 3927 unsigned epnum, maxp;
> 3928 int is_input;
> 3929 long bandwidth;
> 3930 unsigned multi;
> 3931
> 3932 /*
> 3933 * this might be a "high bandwidth" highspeed endpoint,
> 3934 * as encoded in the ep descriptor's wMaxPacket field
> 3935 */
> 3936 epnum = usb_pipeendpoint(pipe);
> 3937 is_input = usb_pipein(pipe) ? USB_DIR_IN : 0;
> 3938 maxp = usb_maxpacket(dev, pipe, !is_input);
> 3939 if (is_input)
> 3940 buf1 = (1 << 11);
> 3941 else
> 3942 buf1 = 0;
> 3943
> 3944 maxp = max_packet(maxp);
> 3945 multi = hb_mult(maxp);
> 3946 buf1 |= maxp;
> 3947 maxp *= multi;
This is pretty clearly a case of mistaken reuse of a local variable.
The argument to hb_mult() should be the output from usb_maxpacket(),
not the result of the max_packet() calculation.
> 3948
> 3949 stream->buf0 = cpu_to_hc32(fotg210, (epnum << 8) | dev->devnum);
> 3950 stream->buf1 = cpu_to_hc32(fotg210, buf1);
> 3951 stream->buf2 = cpu_to_hc32(fotg210, multi);
>
> The problem is these two defines:
>
> #define max_packet(wMaxPacketSize) ((wMaxPacketSize) & 0x07ff)
> #define hb_mult(wMaxPacketSize) (1 + (((wMaxPacketSize) >> 11) & 0x03))
>
> 0x07ff >> 11 is always zero so multi is always 1.
>
> Should we pass the original value that usb_maxpacket() returned instead
> of the masked value?
Yes. I suggest introducing a new local variable and using it in place
of maxp in lines 3938, 3944 (the second occurrence), and 3945.
Alan Stern
> regards,
> dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [bug report] usb: host: Faraday fotg210-hcd driver
2020-02-11 15:24 ` Alan Stern
@ 2020-02-11 15:47 ` Alan Stern
0 siblings, 0 replies; 3+ messages in thread
From: Alan Stern @ 2020-02-11 15:47 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-usb, john453
On Tue, 11 Feb 2020, Alan Stern wrote:
> On Tue, 11 Feb 2020, Dan Carpenter wrote:
>
> > Hello USB devs,
> >
> > The patch 7d50195f6c50: "usb: host: Faraday fotg210-hcd driver" from
> > Jul 29, 2013, leads to the following static checker warning:
> >
> > drivers/usb/host/fotg210-hcd.c:3945 iso_stream_init()
> > warn: mask and shift to zero
> >
> > drivers/usb/host/fotg210-hcd.c
> > 3922 static void iso_stream_init(struct fotg210_hcd *fotg210,
> > 3923 struct fotg210_iso_stream *stream, struct usb_device *dev,
> > 3924 int pipe, unsigned interval)
> > 3925 {
> > 3926 u32 buf1;
> > 3927 unsigned epnum, maxp;
> > 3928 int is_input;
> > 3929 long bandwidth;
> > 3930 unsigned multi;
> > 3931
> > 3932 /*
> > 3933 * this might be a "high bandwidth" highspeed endpoint,
> > 3934 * as encoded in the ep descriptor's wMaxPacket field
> > 3935 */
> > 3936 epnum = usb_pipeendpoint(pipe);
> > 3937 is_input = usb_pipein(pipe) ? USB_DIR_IN : 0;
> > 3938 maxp = usb_maxpacket(dev, pipe, !is_input);
> > 3939 if (is_input)
> > 3940 buf1 = (1 << 11);
> > 3941 else
> > 3942 buf1 = 0;
> > 3943
> > 3944 maxp = max_packet(maxp);
> > 3945 multi = hb_mult(maxp);
> > 3946 buf1 |= maxp;
> > 3947 maxp *= multi;
>
> This is pretty clearly a case of mistaken reuse of a local variable.
> The argument to hb_mult() should be the output from usb_maxpacket(),
> not the result of the max_packet() calculation.
Oops, my mistake, sorry. I should have read the source more carefully
before answering.
The max_packet() macro in line 3944 does nothing, since it is only a
mask with 0x07ff and usb_maxpacket() (which calls usb_endpoint_maxp
internally) already performs this mask.
> > 3948
> > 3949 stream->buf0 = cpu_to_hc32(fotg210, (epnum << 8) | dev->devnum);
> > 3950 stream->buf1 = cpu_to_hc32(fotg210, buf1);
> > 3951 stream->buf2 = cpu_to_hc32(fotg210, multi);
> >
> > The problem is these two defines:
> >
> > #define max_packet(wMaxPacketSize) ((wMaxPacketSize) & 0x07ff)
> > #define hb_mult(wMaxPacketSize) (1 + (((wMaxPacketSize) >> 11) & 0x03))
> >
> > 0x07ff >> 11 is always zero so multi is always 1.
> >
> > Should we pass the original value that usb_maxpacket() returned instead
> > of the masked value?
>
> Yes. I suggest introducing a new local variable and using it in place
> of maxp in lines 3938, 3944 (the second occurrence), and 3945.
So the actual right thing to do is to convert the pipe value to a
usb_endpoint_descriptor *, say by way of usb_pipe_endpoint(). Then
maxp and multi can be calculated from the descriptor via
usb_endpoint_maxp() and usb_endpoint_maxp_mult().
Alan Stern
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-02-11 15:03 [bug report] usb: host: Faraday fotg210-hcd driver Dan Carpenter
2020-02-11 15:24 ` Alan Stern
2020-02-11 15:47 ` Alan Stern
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