linux-kernel - Re: [PATCH] i915: fix build on gcc7

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Date:   Thu, 01 Jun 2017 14:53:51 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Aleksa Sarai <asarai@...e.de>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Aleksa Sarai <asarai@...e.de>
Subject: Re: [PATCH] i915: fix build on gcc7

On Thu, 01 Jun 2017, Aleksa Sarai <asarai@...e.de> wrote:
> With gcc7, the conditional usage of (port == PORT_A ? PORT_C : PORT_A)
> triggers -Werror=int-in-bool-context which breaks the build. Instead,
> use a temporary port_other variable that avoids hitting this error.
>
>   % gcc --version
>   gcc (SUSE Linux) 7.1.1 20170517 [gcc-7-branch revision 248152]
>   Copyright (C) 2017 Free Software Foundation, Inc.
>   This is free software; see the source for copying conditions.  There is NO
>   warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>   % make -j8 drivers/gpu/drm/i915/intel_dsi.o
>   In file included from drivers/gpu/drm/i915/intel_dsi.c:34:0:
>   drivers/gpu/drm/i915/intel_dsi.c: In function ‘intel_dsi_prepare’:
>   drivers/gpu/drm/i915/intel_dsi.c:1487:23: error: ?: using integer constants in boolean context [-Werror=int-in-bool-context]
>          PORT_A ? PORT_C : PORT_A),
>   drivers/gpu/drm/i915/i915_drv.h:3909:76: note: in definition of macro ‘I915_WRITE’
>    #define I915_WRITE(reg, val) dev_priv->uncore.funcs.mmio_writel(dev_priv, (reg), (val), true)
>                                                                               ^~~
>   drivers/gpu/drm/i915/i915_reg.h:8280:32: note: in expansion of macro ‘_MMIO’
>    #define _MMIO_MIPI(port, a, c) _MMIO(_MIPI_PORT(port, a, c))
>                                   ^~~~~
>   drivers/gpu/drm/i915/i915_reg.h:8280:38: note: in expansion of macro ‘_MIPI_PORT’
>    #define _MMIO_MIPI(port, a, c) _MMIO(_MIPI_PORT(port, a, c))
>                                         ^~~~~~~~~~
>   drivers/gpu/drm/i915/i915_reg.h:8624:32: note: in expansion of macro ‘_MMIO_MIPI’
>    #define MIPI_INIT_COUNT(port)  _MMIO_MIPI(port, _MIPIA_INIT_COUNT, _MIPIC_INIT_COUNT)
>                                   ^~~~~~~~~~
>   drivers/gpu/drm/i915/intel_dsi.c:1486:15: note: in expansion of macro ‘MIPI_INIT_COUNT’
>       I915_WRITE(MIPI_INIT_COUNT(port ==
>                  ^~~~~~~~~~~~~~~
>
> Signed-off-by: Aleksa Sarai <asarai@...e.de>

This is probably already fixed in drm-next by

commit 0ad4dc887d4168448e8c801aa4edd8fe1e0bd534
Author: Hans de Goede <hdegoede@...hat.com>
Date:   Thu May 18 13:06:44 2017 +0200

    drm/i915: Fix new -Wint-in-bool-context gcc compiler warning

which I also think is a more sensible fix than this one.

BR,
Jani.


> ---
>  drivers/gpu/drm/i915/intel_dsi.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 54030b68406a..53e717e7b811 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -1476,14 +1476,15 @@ static void intel_dsi_prepare(struct intel_encoder *intel_encoder,
>  				txclkesc(intel_dsi->escape_clk_div, 100));
>  
>  		if (IS_GEN9_LP(dev_priv) && (!intel_dsi->dual_link)) {
> +			enum port port_other = port == PORT_A ? PORT_C : PORT_A;
> +
>  			/*
>  			 * BXT spec says write MIPI_INIT_COUNT for
>  			 * both the ports, even if only one is
>  			 * getting used. So write the other port
>  			 * if not in dual link mode.
>  			 */
> -			I915_WRITE(MIPI_INIT_COUNT(port ==
> -						PORT_A ? PORT_C : PORT_A),
> +			I915_WRITE(MIPI_INIT_COUNT(port_other),
>  					intel_dsi->init_count);
>  		}

-- 
Jani Nikula, Intel Open Source Technology Center