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Date:   Thu, 05 Mar 2020 01:46:03 -0800
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Subject: Re: [PATCH] x86/cpuid: Use macro instead of number in cpuid_read()
To:     Yu Chen <chen.yu@easystack.cn>, tglx@linutronix.de
CC:     linux-kernel@vger.kernel.org, x86@kernel.org, yuchen1988@aliyun.com
From:   hpa@zytor.com
Message-ID: <83699764-1956-4C58-8347-41A29A0687C4@zytor.com>
Sender: linux-kernel-owner@vger.kernel.org
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On March 5, 2020 1:33:18 AM PST, Yu Chen <chen=2Eyu@easystack=2Ecn> wrote:
>Make and use macro CHUNK_SIZE, instead of numeric value 16 in
>cpuid_read()=2E
>
>Signed-off-by: Yu Chen <chen=2Eyu@easystack=2Ecn>
>---
> arch/x86/kernel/cpuid=2Ec | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
>diff --git a/arch/x86/kernel/cpuid=2Ec b/arch/x86/kernel/cpuid=2Ec
>index 3492aa36b=2E=2Ef7d7e0ef7 100644
>--- a/arch/x86/kernel/cpuid=2Ec
>+++ b/arch/x86/kernel/cpuid=2Ec
>@@ -48,6 +48,9 @@ struct cpuid_regs_done {
> 	struct completion done;
> };
>=20
>+/* cpuid must be read in chunks of 16 bytes */
>+#define CHUNK_SIZE	16
>+
> static void cpuid_smp_cpuid(void *cmd_block)
> {
> 	struct cpuid_regs_done *cmd =3D cmd_block;
>@@ -69,11 +72,11 @@ static ssize_t cpuid_read(struct file *file, char
>__user *buf,
> 	ssize_t bytes =3D 0;
> 	int err =3D 0;
>=20
>-	if (count % 16)
>+	if (count % CHUNK_SIZE)
> 		return -EINVAL;	/* Invalid chunk size */
>=20
> 	init_completion(&cmd=2Edone);
>-	for (; count; count -=3D 16) {
>+	for (; count; count -=3D CHUNK_SIZE) {
> 		call_single_data_t csd =3D {
> 			=2Efunc =3D cpuid_smp_cpuid,
> 			=2Einfo =3D &cmd,
>@@ -86,12 +89,12 @@ static ssize_t cpuid_read(struct file *file, char
>__user *buf,
> 		if (err)
> 			break;
> 		wait_for_completion(&cmd=2Edone);
>-		if (copy_to_user(tmp, &cmd=2Eregs, 16)) {
>+		if (copy_to_user(tmp, &cmd=2Eregs, CHUNK_SIZE)) {
> 			err =3D -EFAULT;
> 			break;
> 		}
>-		tmp +=3D 16;
>-		bytes +=3D 16;
>+		tmp +=3D CHUNK_SIZE;
>+		bytes +=3D CHUNK_SIZE;
> 		*ppos =3D ++pos;
> 		reinit_completion(&cmd=2Edone);
> 	}

It would make more sense to define a structure and add it to a uapi header=
=2E
--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E