linux-kernel - [bug-report] Smatch warns unsigned comparison with zero in dw_mipi_dsi_rockchip_set

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Message-ID: <364c0959-c82f-a93c-df02-87a04e1c2cea@oracle.com>
Date:   Mon, 17 Oct 2022 20:33:28 +0530
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     macroalpha82@...il.com, hjc@...k-chips.com, heiko@...ech.de
Cc:     airlied@...il.com, Dan Carpenter <dan.carpenter@...cle.com>,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        harshit.m.mogalapalli@...il.com
Subject: [bug-report] Smatch warns unsigned comparison with zero in
 dw_mipi_dsi_rockchip_set_lcdsel()

Hi,


Smatch warns:
drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c:755 
dw_mipi_dsi_rockchip_set_lcdsel() warn: unsigned 
'dsi->cdata->lcdsel_grf_reg'
is never less than zero.

static void dw_mipi_dsi_rockchip_set_lcdsel(struct dw_mipi_dsi_rockchip 
*dsi,
                                             int mux)
{
         if (dsi->cdata->lcdsel_grf_reg < 0)
                 regmap_write(dsi->grf_regmap, dsi->cdata->lcdsel_grf_reg,
                         mux ? dsi->cdata->lcdsel_lit : 
dsi->cdata->lcdsel_big);
}

'dsi->cdata->lcdsel_grf_reg' is of u32 type, it can never be less than zero.
So the above if condition is an impossible one.

Note: 'lcdsel_grf_reg' is set to -1 at other places.


Thanks,
Harshit