[bug report] drm/panel: Add BOE BF060Y8M-AJ0 5.99" AMOLED panel driver

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello AngeloGioacchino Del Regno,

The patch a19125a28112: "drm/panel: Add BOE BF060Y8M-AJ0 5.99" AMOLED
panel driver" from Sep 1, 2021, leads to the following (unpublished)
Smatch static checker warning:

drivers/gpu/drm/panel/panel-boe-bf060y8m-aj0.c:317 boe_bf060y8m_aj0_init_vregs() info: return a literal instead of 'ret'
drivers/gpu/drm/panel/panel-boe-bf060y8m-aj0.c:322 boe_bf060y8m_aj0_init_vregs() info: return a literal instead of 'ret'
drivers/gpu/drm/panel/panel-boe-bf060y8m-aj0.c:327 boe_bf060y8m_aj0_init_vregs() info: return a literal instead of 'ret'
drivers/gpu/drm/panel/panel-boe-bf060y8m-aj0.c:332 boe_bf060y8m_aj0_init_vregs() info: return a literal instead of 'ret'
drivers/gpu/drm/panel/panel-boe-bf060y8m-aj0.c:338 boe_bf060y8m_aj0_init_vregs() info: return a literal instead of 'ret'

drivers/gpu/drm/panel/panel-boe-bf060y8m-aj0.c
    296 static int boe_bf060y8m_aj0_init_vregs(struct boe_bf060y8m_aj0 *boe,
    297                                        struct device *dev)
    298 {
    299         struct regulator *vreg;
    300         int ret;
    301 
    302         boe->vregs[BF060Y8M_VREG_VCC].supply = "vcc";
    303         boe->vregs[BF060Y8M_VREG_VDDIO].supply = "vddio";
    304         boe->vregs[BF060Y8M_VREG_VCI].supply = "vci";
    305         boe->vregs[BF060Y8M_VREG_EL_VDD].supply = "elvdd";
    306         boe->vregs[BF060Y8M_VREG_EL_VSS].supply = "elvss";
    307         ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(boe->vregs),
    308                                       boe->vregs);
    309         if (ret < 0) {
    310                 dev_err(dev, "Failed to get regulators: %d\n", ret);
    311                 return ret;
    312         }
    313 
    314         vreg = boe->vregs[BF060Y8M_VREG_VCC].consumer;
    315         ret = regulator_is_supported_voltage(vreg, 2700000, 3600000);
    316         if (!ret)
                ^^^^^^^^^

--> 317                 return ret;

It's more clear to "return 0;" instead of "return ret;"

The documentation for regulator_is_supported_voltage() says it returns
bool but actually it returns negatives for if regulator_get_voltage()
fails and one for if it's supported and zero for when it's not.

These if (!ret) seem wrong.

    318 
    319         vreg = boe->vregs[BF060Y8M_VREG_VDDIO].consumer;
    320         ret = regulator_is_supported_voltage(vreg, 1620000, 1980000);
    321         if (!ret)
                ^^^^^^^^^

    322                 return ret;
    323 
    324         vreg = boe->vregs[BF060Y8M_VREG_VCI].consumer;
    325         ret = regulator_is_supported_voltage(vreg, 2600000, 3600000);
    326         if (!ret)
                ^^^^^^^^^

    327                 return ret;
    328 
    329         vreg = boe->vregs[BF060Y8M_VREG_EL_VDD].consumer;
    330         ret = regulator_is_supported_voltage(vreg, 4400000, 4800000);
    331         if (!ret)
                ^^^^^^^^^

    332                 return ret;
    333 
    334         /* ELVSS is negative: -5.00V to -1.40V */
    335         vreg = boe->vregs[BF060Y8M_VREG_EL_VSS].consumer;
    336         ret = regulator_is_supported_voltage(vreg, 1400000, 5000000);
    337         if (!ret)
                ^^^^^^^^

    338                 return ret;
    339 
    340         /*
    341          * Set min/max rated current, known only for VCI and VDDIO and,
    342          * in case of failure, just go on gracefully, as this step is not
    343          * guaranteed to succeed on all regulator HW but do a debug print
    344          * to inform the developer during debugging.
    345          * In any case, these two supplies are also optional, so they may
    346          * be fixed-regulator which, at the time of writing, does not
    347          * support fake current limiting.
    348          */
    349         vreg = boe->vregs[BF060Y8M_VREG_VDDIO].consumer;
    350         ret = regulator_set_current_limit(vreg, 1500, 2500);
    351         if (ret)
    352                 dev_dbg(dev, "Current limit cannot be set on %s: %d\n",
    353                         boe->vregs[1].supply, ret);
    354 
    355         vreg = boe->vregs[BF060Y8M_VREG_VCI].consumer;
    356         ret = regulator_set_current_limit(vreg, 20000, 40000);
    357         if (ret)
    358                 dev_dbg(dev, "Current limit cannot be set on %s: %d\n",
    359                         boe->vregs[2].supply, ret);
    360 
    361         return 0;
    362 }

regards,
dan carpenter