linux-kernel - panasonic-laptop driver oddity

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Message-ID: <20090115154717.GC6896@shadowen.org>
Date:	Thu, 15 Jan 2009 15:47:17 +0000
From:	Andy Whitcroft <apw@...onical.com>
To:	Harald Welte <laforge@...monks.org>
Cc:	linux-kernel@...r.kernel.org
Subject: panasonic-laptop driver oddity

We have been looking at your panasonic-laptop driver with a view to
back porting it to 2.6.27, and the following inconsistancy was pointed
out to me.  In bl_set_status() we ensure that bright is no lower than
sinf[SINF_AC_MIN_BRIGHT] and sinf[SINF_DC_MIN_BRIGHT], and then check if
it is lower than sinf[SINF_AC_MIN_BRIGHT].  That seems redundant.

    static int bl_set_status(struct backlight_device *bd)
    {
        struct pcc_acpi *pcc = bl_get_data(bd);
        int bright = bd->props.brightness;
        int rc;

        if (!acpi_pcc_retrieve_biosdata(pcc, pcc->sinf))
                return -EIO;

        if (bright < pcc->sinf[SINF_AC_MIN_BRIGHT])
                bright = pcc->sinf[SINF_AC_MIN_BRIGHT];

        if (bright < pcc->sinf[SINF_DC_MIN_BRIGHT])
                bright = pcc->sinf[SINF_DC_MIN_BRIGHT];

        if (bright < pcc->sinf[SINF_AC_MIN_BRIGHT] ||
            bright > pcc->sinf[SINF_AC_MAX_BRIGHT])
                return -EINVAL;

We could not decide if this was simply belt and braces to constrain the
value, or if this should be a check against sinf[SINF_DC_MAX_BRIGHT].
Perhaps you could clarify?

-apw
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