netdev - Re: [PATCH v3 6/7] venus: Make debug infrastructure more flexible

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Message-ID: <ed7dd5b4-aace-7558-d012-fb16ce8c92d6@linaro.org>
Date:   Thu, 11 Jun 2020 14:31:07 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>,
        Joe Perches <joe@...ches.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-acpi@...r.kernel.org,
        netdev@...r.kernel.org, Jason Baron <jbaron@...mai.com>
Subject: Re: [PATCH v3 6/7] venus: Make debug infrastructure more flexible


On 6/11/20 1:52 PM, Daniel Thompson wrote:
> On Wed, Jun 10, 2020 at 11:42:43PM -0700, Joe Perches wrote:
>> On Thu, 2020-06-11 at 08:26 +0200, Greg Kroah-Hartman wrote:
>>> On Wed, Jun 10, 2020 at 01:23:56PM -0700, Joe Perches wrote:
>>>> On Wed, 2020-06-10 at 12:49 -0700, Joe Perches wrote:
>>>>> On Wed, 2020-06-10 at 15:37 +0200, Greg Kroah-Hartman wrote:
>>>>>> Please work with the infrastructure we have, we have spent a lot of time
>>>>>> and effort to make it uniform to make it easier for users and
>>>>>> developers.
>>>>>
>>>>> Not quite.
>>>>>
>>>>> This lack of debug grouping by type has been a
>>>>> _long_ standing issue with drivers.
>>>>>
>>>>>> Don't regress and try to make driver-specific ways of doing
>>>>>> things, that way lies madness...
>>>>>
>>>>> It's not driver specific, it allows driver developers to
>>>>> better isolate various debug states instead of keeping
>>>>> lists of specific debug messages and enabling them
>>>>> individually.
>>>>
>>>> For instance, look at the homebrew content in
>>>> drivers/gpu/drm/drm_print.c that does _not_ use
>>>> dynamic_debug.
>>>>
>>>> MODULE_PARM_DESC(debug, "Enable debug output, where each bit enables a debug category.\n"
>>>> "\t\tBit 0 (0x01)  will enable CORE messages (drm core code)\n"
>>>> "\t\tBit 1 (0x02)  will enable DRIVER messages (drm controller code)\n"
>>>> "\t\tBit 2 (0x04)  will enable KMS messages (modesetting code)\n"
>>>> "\t\tBit 3 (0x08)  will enable PRIME messages (prime code)\n"
>>>> "\t\tBit 4 (0x10)  will enable ATOMIC messages (atomic code)\n"
>>>> "\t\tBit 5 (0x20)  will enable VBL messages (vblank code)\n"
>>>> "\t\tBit 7 (0x80)  will enable LEASE messages (leasing code)\n"
>>>> "\t\tBit 8 (0x100) will enable DP messages (displayport code)");
>>>> module_param_named(debug, __drm_debug, int, 0600);
>>>>
>>>> void drm_dev_dbg(const struct device *dev, enum drm_debug_category category,
>>>> 		 const char *format, ...)
>>>> {
>>>> 	struct va_format vaf;
>>>> 	va_list args;
>>>>
>>>> 	if (!drm_debug_enabled(category))
>>>> 		return;
>>>
>>> Ok, and will this proposal be able to handle stuff like this?
>>
>> Yes, that's the entire point.
> 
> Currently I think there not enough "levels" to map something like
> drm.debug to the new dyn dbg feature. I don't think it is intrinsic
> but I couldn't find the bit of the code where the 5-bit level in struct
> _ddebug is converted from a mask to a bit number and vice-versa.

Here [1] is Joe's initial suggestion. But I decided that bitmask is a
good start for the discussion.

I guess we can add new member uint "level" in struct _ddebug so that we
can cover more "levels" (types, groups).

-- 
regards,
Stan

[1] https://lkml.org/lkml/2020/5/21/915