linux-kernel - Re: [PATCH] ALSA: hda/ca0132: work around clang -Wuninitialized warning

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Date:   Fri, 22 Mar 2019 16:00:19 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Arnd Bergmann" <arnd@...db.de>
Cc:     "Connor McAdams" <conmanx360@...il.com>,
        "Takashi Sakamoto" <o-takashi@...amocchi.jp>,
        <alsa-devel@...a-project.org>,
        "Alastair Bridgewater" <alastair.bridgewater@...il.com>,
        "Nathan Chancellor" <natechancellor@...il.com>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        <clang-built-linux@...glegroups.com>,
        "Jaroslav Kysela" <perex@...ex.cz>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: hda/ca0132: work around clang -Wuninitialized warning

On Fri, 22 Mar 2019 15:06:28 +0100,
Arnd Bergmann wrote:
> 
> When CONFIG_PCI is disabled, clang gets confused about the
> control flow of the switch() statement always ending up
> in the default case, and warns:
> 
> sound/pci/hda/patch_ca0132.c:7558:6: error: variable 'fw_entry' is used uninitialized whenever 'if' condition is false
>       [-Werror,-Wsometimes-uninitialized]
>         if (!spec->alt_firmware_present) {
>             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> sound/pci/hda/patch_ca0132.c:7565:42: note: uninitialized use occurs here
>         dsp_os_image = (struct dsp_image_seg *)(fw_entry->data);
>                                                 ^~~~~~~~
> sound/pci/hda/patch_ca0132.c:7558:2: note: remove the 'if' if its condition is always true
>         if (!spec->alt_firmware_present) {
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> sound/pci/hda/patch_ca0132.c:7521:33: note: initialize the variable 'fw_entry' to silence this warning
>         const struct firmware *fw_entry;
>                                        ^
>                                         = NULL
> 
> Adding an explicit check for CONFIG_PCI avoids the issue.
> Unfortunately this is not very intuitive here.
> 
> Link: https://bugs.llvm.org/show_bug.cgi?id=41197#c1
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> Any suggestions for other workarounds appreciated. If you can think
> of a better fix, please treat this as a reported-by:

Can it be addressed by the code simplification like below, instead?


thanks,

Takashi

---
 sound/pci/hda/patch_ca0132.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/sound/pci/hda/patch_ca0132.c b/sound/pci/hda/patch_ca0132.c
index 29882bda7632..e1ebc6d5f382 100644
--- a/sound/pci/hda/patch_ca0132.c
+++ b/sound/pci/hda/patch_ca0132.c
@@ -1005,7 +1005,6 @@ struct ca0132_spec {
 	unsigned int scp_resp_header;
 	unsigned int scp_resp_data[4];
 	unsigned int scp_resp_count;
-	bool alt_firmware_present;
 	bool startup_check_entered;
 	bool dsp_reload;
 
@@ -7518,7 +7517,7 @@ static bool ca0132_download_dsp_images(struct hda_codec *codec)
 	bool dsp_loaded = false;
 	struct ca0132_spec *spec = codec->spec;
 	const struct dsp_image_seg *dsp_os_image;
-	const struct firmware *fw_entry;
+	const struct firmware *fw_entry = NULL;
 	/*
 	 * Alternate firmwares for different variants. The Recon3Di apparently
 	 * can use the default firmware, but I'll leave the option in case
@@ -7529,33 +7528,26 @@ static bool ca0132_download_dsp_images(struct hda_codec *codec)
 	case QUIRK_R3D:
 	case QUIRK_AE5:
 		if (request_firmware(&fw_entry, DESKTOP_EFX_FILE,
-					codec->card->dev) != 0) {
+					codec->card->dev) != 0)
 			codec_dbg(codec, "Desktop firmware not found.");
-			spec->alt_firmware_present = false;
-		} else {
+		else
 			codec_dbg(codec, "Desktop firmware selected.");
-			spec->alt_firmware_present = true;
-		}
 		break;
 	case QUIRK_R3DI:
 		if (request_firmware(&fw_entry, R3DI_EFX_FILE,
-					codec->card->dev) != 0) {
+					codec->card->dev) != 0)
 			codec_dbg(codec, "Recon3Di alt firmware not detected.");
-			spec->alt_firmware_present = false;
-		} else {
+		else
 			codec_dbg(codec, "Recon3Di firmware selected.");
-			spec->alt_firmware_present = true;
-		}
 		break;
 	default:
-		spec->alt_firmware_present = false;
 		break;
 	}
 	/*
 	 * Use default ctefx.bin if no alt firmware is detected, or if none
 	 * exists for your particular codec.
 	 */
-	if (!spec->alt_firmware_present) {
+	if (!fw_entry) {
 		codec_dbg(codec, "Default firmware selected.");
 		if (request_firmware(&fw_entry, EFX_FILE,
 					codec->card->dev) != 0)
-- 
2.16.4