linux-kernel - Re: adv748x: missing parens

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Message-ID: <baecb140-986a-da96-665a-0ec581ae2c75@embeddedor.com>
Date:   Tue, 22 Oct 2019 08:02:50 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        kieran.bingham@...asonboard.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: adv748x: missing parens

Hi Dmitry,

Thanks for the report.

On 10/22/19 02:29, Dmitry Vyukov wrote:
> Hi Kieran,
> 
> Building kernel with clang gives me:
> 
> drivers/media/i2c/adv748x/adv748x-afe.c:452:12: warning: operator '?:'
> has lower precedence than '|'; '|' will be evaluated first
> [-Wbitwise-conditional-parentheses]
> 
> ret = sdp_clrset(state, ADV748X_SDP_FRP, ADV748X_SDP_FRP_MASK, enable
> ? ctrl->val - 1 : 0);
> #define sdp_clrset(s, r, m, v) sdp_write(s, r, (sdp_read(s, r) & ~m) | v)
> 
> This is on linux-next commit a722f75b2923b4fd44c17e7255e822ac48fe85f0
> Date:   Tue Oct 22 16:17:17 2019 +1100
>     Add linux-next specific files for 20191022
> 
> It seems sdp_clrset needs some more parens.
> 

Yep. It seems this is enough to fix the issue:

diff --git a/drivers/media/i2c/adv748x/adv748x.h b/drivers/media/i2c/adv748x/adv748x.h
index 5042f9e94aee..fccb388ce179 100644
--- a/drivers/media/i2c/adv748x/adv748x.h
+++ b/drivers/media/i2c/adv748x/adv748x.h
@@ -394,10 +394,10 @@ int adv748x_write_block(struct adv748x_state *state, int client_page,

 #define io_read(s, r) adv748x_read(s, ADV748X_PAGE_IO, r)
 #define io_write(s, r, v) adv748x_write(s, ADV748X_PAGE_IO, r, v)
-#define io_clrset(s, r, m, v) io_write(s, r, (io_read(s, r) & ~m) | v)
+#define io_clrset(s, r, m, v) io_write(s, r, (io_read(s, r) & ~(m)) | (v))

 #define hdmi_read(s, r) adv748x_read(s, ADV748X_PAGE_HDMI, r)
-#define hdmi_read16(s, r, m) (((hdmi_read(s, r) << 8) | hdmi_read(s, r+1)) & m)
+#define hdmi_read16(s, r, m) (((hdmi_read(s, r) << 8) | hdmi_read(s, (r)+1)) & (m))
 #define hdmi_write(s, r, v) adv748x_write(s, ADV748X_PAGE_HDMI, r, v)

 #define repeater_read(s, r) adv748x_read(s, ADV748X_PAGE_REPEATER, r)
@@ -405,11 +405,11 @@ int adv748x_write_block(struct adv748x_state *state, int client_page,

 #define sdp_read(s, r) adv748x_read(s, ADV748X_PAGE_SDP, r)
 #define sdp_write(s, r, v) adv748x_write(s, ADV748X_PAGE_SDP, r, v)
-#define sdp_clrset(s, r, m, v) sdp_write(s, r, (sdp_read(s, r) & ~m) | v)
+#define sdp_clrset(s, r, m, v) sdp_write(s, r, (sdp_read(s, r) & ~(m)) | (v))

 #define cp_read(s, r) adv748x_read(s, ADV748X_PAGE_CP, r)
 #define cp_write(s, r, v) adv748x_write(s, ADV748X_PAGE_CP, r, v)
-#define cp_clrset(s, r, m, v) cp_write(s, r, (cp_read(s, r) & ~m) | v)
+#define cp_clrset(s, r, m, v) cp_write(s, r, (cp_read(s, r) & ~(m)) | (v))

 #define tx_read(t, r) adv748x_read(t->state, t->page, r)
 #define tx_write(t, r, v) adv748x_write(t->state, t->page, r, v)


More on writing safe macros in C:

https://wiki.sei.cmu.edu/confluence/display/c/PRE31-C.+Avoid+side+effects+in+arguments+to+unsafe+macros

--
Gustavo