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Message-ID: <4AFD726E.40101@natemccallum.com> Date: Fri, 13 Nov 2009 09:51:26 -0500 From: Nathaniel McCallum <nathaniel@...emccallum.com> To: Greg KH <greg@...ah.com> CC: linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org Subject: Re: [PATCH] Devices that ignore USB spec generate invalid modaliases On 11/12/2009 08:09 PM, Nathaniel McCallum wrote: > On 11/12/2009 06:42 PM, Greg KH wrote: >> On Wed, Nov 11, 2009 at 03:20:23AM -0500, Nathaniel McCallum wrote: >>> Please CC me as I'm not subscribed to LKML. >>> >>> The current code to generate usb modaliases from usb_device_id assumes >>> that the device's bcdDevice descriptor will actually be in BCD format. >>> While this should be a sane assumption, some devices don't follow spec >>> and just use plain old hex. This causes drivers for these devices to >>> generate invalid modalias lines which will never actually match for the >>> hardware. >>> >>> The following patch adds hex support for bcdDevice in file2alias.c. >>> Drivers for devices which have bcdDevice conforming to BCD will have no >>> change in modalias output. Drivers for devices which don't conform >>> (primarily usb-storage and ibmcam in my initial survey) should now >>> generate valid modaliases. >>> >>> EXAMPLE OUTPUT (ibmcam; space added to highlight change) >>> Old: usb:v0545p800D d030[10-9] dc*dsc*dp*ic*isc*ip* >>> New: usb:v0545p800D d030a dc*dsc*dp*ic*isc*ip* >> >> Huh? The old one had '[]' in it? >> >> What does the bcdDevice for this really look like in the device itself? >> If it is messed up in the descriptor, then how can we know to fix it up >> here? > > The device contains 0x030A (an invalid value since 0x0309 + 1 == 0x0310 > in BCD format) in the bcdDevice descriptor. The driver matches against > this descriptor (see the usb_device_id table in > drivers/media/video/usbvideo/ibmcam.c). > > There are three possible solutions: > 1. Fix the ibmcam driver not to match against bcdDevice. I'm not sure if > this is possible. Nor does it solve the problem for future devices which > may be misprogrammed. > 2. Change *all* usb modaliases to be generated assuming hex ranges. This > makes file2alias.c a little simpler at the cost of changing a large > number of existing modaliases. The impact of this change is potentially > large. > 3. My solution, which is to detect if either bcdDevice_lo or > bcdDevice_hi is in hexadecimal rather than BCD format. We do this by > checking each character to see if it is above 0x9. If either of these > fields is in hex format, we switch into hex mode and render the modalias > appropriately. This also has some potential impact on userspace tools, > however, since currently the only modalias that is affected is ibmcam, > the change is measurably small in impact. > > The second bug (related here: http://lkml.org/lkml/2009/11/11/245) is > just simply a bug in the modalias generation code. Namely, 0x59 + 1 == > 0x60 in BCD format, not 0x5A. Therefore, you cannot rely on i++ to > increment. Fixing it has no impact other than fixing a broken modalias > (which occurs in usb-storage). Just in case it is helpful, here is a diff between the old modules.alias and the new modules.alias generated with my patches applied. The usb_storage line is fixed by the increment patch. The ibmcam lines are fixed by the bcd/hex patch. --- modules.alias.old 2009-11-13 09:46:36.191640578 -0500 +++ modules.alias.fixed 2009-11-13 09:46:36.549891821 -0500 @@ -345,7 +345,6 @@ alias usb:v041Ep4064d*dc*dsc*dp*ic*isc*ip* gspca_ov519 alias usb:v041Ep4068d*dc*dsc*dp*ic*isc*ip* gspca_ov519 alias usb:v0420p0001d0100dc*dsc*dp*ic*isc*ip* usb_storage -alias usb:v0421p0019d05[10-9]*dc*dsc*dp*ic*isc*ip* usb_storage alias usb:v0421p0019d059[2-9]dc*dsc*dp*ic*isc*ip* usb_storage alias usb:v0421p0019d060*dc*dsc*dp*ic*isc*ip* usb_storage alias usb:v0421p0019d0610dc*dsc*dp*ic*isc*ip* usb_storage @@ -1021,12 +1020,12 @@ alias usb:v0543p1921d*dc*dsc*dp*ic*isc*ip* ipaq alias usb:v0543p1922d*dc*dsc*dp*ic*isc*ip* ipaq alias usb:v0543p1923d*dc*dsc*dp*ic*isc*ip* ipaq -alias usb:v0545p8002d030[10-9]dc*dsc*dp*ic*isc*ip* ibmcam -alias usb:v0545p800Cd030[10-9]dc*dsc*dp*ic*isc*ip* ibmcam -alias usb:v0545p800Dd030[10-9]dc*dsc*dp*ic*isc*ip* ibmcam +alias usb:v0545p8002d030Adc*dsc*dp*ic*isc*ip* ibmcam +alias usb:v0545p800Cd030Adc*dsc*dp*ic*isc*ip* ibmcam +alias usb:v0545p800Dd030Adc*dsc*dp*ic*isc*ip* ibmcam alias usb:v0545p8080d0002dc*dsc*dp*ic*isc*ip* ibmcam -alias usb:v0545p8080d030[10-9]dc*dsc*dp*ic*isc*ip* ibmcam alias usb:v0545p8080d0301dc*dsc*dp*ic*isc*ip* ibmcam +alias usb:v0545p8080d030Adc*dsc*dp*ic*isc*ip* ibmcam alias usb:v0545p808Bd*dc*dsc*dp*ic*isc*ip* gspca_tv8532 alias usb:v0545p8333d*dc*dsc*dp*ic*isc*ip* gspca_tv8532 alias usb:v0546p3155d*dc*dsc*dp*ic*isc*ip* gspca_sunplus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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