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    SubjectRe: [PATCH 1/2] drm: Only #define DEBUG if CONFIG_DYNAMIC_DEBUG is disabled
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    On 2018-12-06 10:12 a.m., Chris Wilson wrote:
    > Quoting Zhang, Jerry(Junwei) (2018-12-06 02:40:42)
    >> On 12/6/18 12:56 AM, Michel Dänzer wrote:
    >>> From: Michel Dänzer <michel.daenzer@amd.com>
    >>>
    >>> The following cases are possible for pr_debug():
    >>>
    >>> 1. CONFIG_DYNAMIC_DEBUG disabled
    >>> a) DEBUG not defined: pr_debug() translates to no_printk(...), i.e.
    >>> it never generates any output.
    >>> b) DEBUG defined: pr_debug() translates to printk(KERN_DEBUG ...),
    >>> i.e. it generates output which doesn't appear in dmesg by default,
    >>> can be enabled dynamically.
    >>>
    >>> 2. CONFIG_DYNAMIC_DEBUG enabled: pr_debug() translates to
    >>> dynamic_pr_debug()
    >>> a) DEBUG not defined: dynamic_pr_debug() generates no output by
    >>> default, can be enabled dynamically.
    >>> b) DEBUG defined: dynamic_pr_debug() generates output by default,
    >>> can be disabled dynamically.
    >>>
    >>> The intention for drm_debug_printer() is to generate output which
    >>> doesn't appear in dmesg by default, but can be enabled dynamically, i.e.
    >>> cases 1b) and 2a). However, defining DEBUG unconditionally gave us 2b)
    >>> instead of 2a) with CONFIG_DYNAMIC_DEBUG enabled.
    >>>
    >>> Fixes: 79a5ad2fdb3c ("drm: Enable pr_debug() for drm_printer")
    >>> Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
    >> Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
    >
    > At the cost of 1a? Nah.

    We still #define DEBUG if CONFIG_DYNAMIC_DEBUG isn't defined, so it's
    still 1b), not 1a).


    --
    Earthling Michel Dänzer | http://www.amd.com
    Libre software enthusiast | Mesa and X developer

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