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SubjectRe: [PATCH 2/2] scsi: ufs: use sysfs entry for health info
Date
On Tue, 2017-12-19 at 12:02 -0800, Jaegeuk Kim wrote:
> This patch introduces sysfs entries to show the information.

What information does "the information" refer to?

Regarding the patch title: I think this patch introduces new sysfs attributes
instead of using existing sysfs entries. If so, please reflect this in the patch
title.

> # cat /sys/devices/soc/1da4000.ufshc/health/eol
> # cat /sys/devices/soc/1da4000.ufshc/health/length
> # cat /sys/devices/soc/1da4000.ufshc/health/lifetimeA
> # cat /sys/devices/soc/1da4000.ufshc/health/lifetimeB
> # cat /sys/devices/soc/1da4000.ufshc/health/type

What is the meaning of the above shell commands in the context of the patch
description?

> struct desc_field_offset health_desc_field_name[] = {
> {"bLength", 0x00, BYTE},
> {"bDescriptorType", 0x01, BYTE},
> {"bPreEOLInfo", 0x02, BYTE},
> {"bDeviceLifeTimeEstA", 0x03, BYTE},
> {"bDeviceLifeTimeEstB", 0x04, BYTE}
> };

Why has the above data been mentioned in the patch description?

> bPreEOLInfo
> - 00h: Not defined
> - 01h: Normal
> - 02h: Warning
> - 03h: Critical
>
> bDeviceLifeTimeEstA
> - 00h: Not defined
> - 01h: 0% ~ 10% device life time used
> - 02h: 10% ~ 20% device life time used
> - 03h: 20% ~ 30% device life time used
> - 04h: 30% ~ 40% device life time used
> - 05h: 40% ~ 50% device life time used
> - 06h: 50% ~ 60% device life time used
> - 07h: 60% ~ 70% device life time used
> - 08h: 70% ~ 80% device life time used
> - 09h: 80% ~ 90% device life time used
> - 0Ah: 90% ~ 100% device life time used
> - 0Bh: Exceeded its maximum estimated device life time

Again, why has the above information been mentioned in the patch description?

> +static ssize_t health_attr_show(struct device *dev,
> + struct health_attr *attr, char *buf)
> +{
> + struct ufs_hba *hba = dev_get_drvdata(dev);
> + int buff_len = hba->desc_size.health_desc;
> + u8 desc_buf[hba->desc_size.health_desc];

Is desc_buf[] a variable-length array? If so, how big can
hba->desc_size.health_desc be? Can that number have a negative value?

> + return scnprintf(buf, PAGE_SIZE, "0x%02x", desc_buf[attr->bytes]);

Please check whether attr->bytes falls inside the bounds of the desc_buf[] array
before using that value as an index.

> +#define HEALTH_ATTR_RO(_name, _bytes) \
> +static struct health_attr ufs_health_##_name = { \
> + .attr = {.name = __stringify(_name), .mode = 0444}, \
> + .show = health_attr_show, \
> + .bytes = _bytes, \
> +}
> +
> +HEALTH_ATTR_RO(length, 0);
> +HEALTH_ATTR_RO(type, 1);
> +HEALTH_ATTR_RO(eol, 2);
> +HEALTH_ATTR_RO(lifetimeA, 3);
> +HEALTH_ATTR_RO(lifetimeB, 4);

The above makes clear that the value stored in the structure member with the name
"bytes" represents an array index. Please choose a better name for that structure
member.

Additionally, since this patch introduces new sysfs attributes, why doesn't it
add any documentation under Documentation/ABI/?

Thanks,

Bart.
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