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Date: Thu, 21 Jul 2011 12:51:18 -0500
From: Scott Wood <scottwood@freescale.com>
Message-ID: <20110721125118.4e64ec21@schlenkerla.am.freescale.net>
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Subject: Re: [Qemu-devel] [PATCH 14/23] PPC: KVM: Add generic function to
 read host clockfreq
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To: Alexander Graf <agraf@suse.de>
Cc: QEMU-devel Developers <qemu-devel@nongnu.org>

On Thu, 21 Jul 2011 03:27:25 +0200
Alexander Graf <agraf@suse.de> wrote:

> +/* Try to find a device tree node for a CPU with clock-frequency property */
> +static int kvmppc_find_cpu_dt(char *buf, int buf_len)
> +{
> +    struct dirent *dirp;
> +    DIR *dp;
> +
> +    if ((dp = opendir(PROC_DEVTREE_CPU)) == NULL) {
> +        printf("Can't open directory " PROC_DEVTREE_CPU "\n");
> +        return -1;
> +    }
> +
> +    buf[0] = '\0';
> +    while ((dirp = readdir(dp)) != NULL) {
> +        FILE *f;
> +        snprintf(buf, buf_len, "%s%s/clock-frequency", PROC_DEVTREE_CPU,
> +                 dirp->d_name);
> +        f = fopen(buf, "r");
> +        if (f) {
> +            snprintf(buf, buf_len, "%scpus/%s", PROC_DEVTREE_CPU, dirp->d_name);
> +            fclose(f);
> +            break;
> +        }
> +        buf[0] = '\0';
> +    }
> +    closedir(dp);
> +    if (buf[0] == '\0') {
> +        printf("Unknown host!\n");
> +        return -1;
> +    }

"Unknown host!" is a little vague for an error message.

> +uint32_t kvmppc_get_clockfreq(void)
> +{
> +    char buf[512];
> +    uint32_t tb;
> +    FILE *f;
> +    int len;
> +
> +    if (kvmppc_find_cpu_dt(buf, sizeof(buf))) {
> +        return 0;
> +    }
> +
> +    snprintf(buf, sizeof(buf), "%s/clock-frequency", buf);
> +
> +    f = fopen(buf, "rb");
> +    if (!f) {
> +        return -1;
> +    }
> +
> +    len = fread(&tb, sizeof(tb), 1, f);
> +    if (len != 1) {
> +        goto err;
> +    }
> +
> +    return tb;
> +err:
> +    fclose(f);
> +    return 0;
> +}

Need to convert endian from big to host.  Also, the frequency can be 64-bit.

-Scott