Re: Kernel Debugging Support

[Austin S Hemmelgarn]

On 2014-08-04 10:21, Alan Stern wrote:
> On Mon, 4 Aug 2014, Austin S Hemmelgarn wrote:
> 
>> On 2014-08-02 09:48, Alan Stern wrote:
>>> On Sat, 2 Aug 2014, Nick Krause wrote:
>>>
>>>> Hey Sharp,
>>>> After reading around seems people want support for usb debugging in
>>>> kgdb or other usb based solutions.
>>>> If you and the other developers are able to help me out a bit as I am
>>>> new I can definitively write this
>>>> area of kgdb support.
>>>
>>> Doesn't kgdb already support USB for debugging?
>>>
>>> Alan Stern
>>
>> AFAICT, on x86 it only supports using either a console capable serial
>> port (so you could do that over USB if you have USB serial console
>> support built-in, but most people I know don't compile that in, and in
>> fact that is the only reason that i compile USB serial support in
>> instead of making it a module), and an AT compatible keyboard with any
>> console option.
> 
> What about with a USB debugging device (CONFIG_EARLY_PRINTK_DBGP)?  
> That's how debugging over USB is _supposed_ to be done.
Yes, except those are really expensive, and on some it's pretty easy if
you don't know what you are doing to really screw things up.
> 
>>  It would be really nice to have USB keyboard support in
>> there so that you don't have to reboot with special options and extra
>> hardware plugged in to get to the debugger, although doing something
>> that supports more than just the HID boot protocol will probably be tricky.
> 
> Is there some reason why kgdb doesn't simply use the kernel's input 
> layer?  If there is, that same reason probably prevents it from using 
> USB.
> 
I believe it's to minimize the in-kernel dependencies.

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