Minor improvement to acpiconf

[Nate Lawson]

M. Warner Losh wrote:
> In message: <4199A260.3020001 at root.org>
>             Nate Lawson <nate at root.org> writes:
> 
> : >  	acpifd = open(ACPIDEV, O_RDWR);
> : >  	if (acpifd == -1){
> : > @@ -117,6 +117,17 @@
> : >  	printf("Type:\t\t\t%s\n", battio.bif.type);
> : >  	printf("OEM info:\t\t%s\n", battio.bif.oeminfo);
> : >  
> : > +	if (ioctl(acpifd, ACPIIO_CMBAT_GET_BST, &battio) == -1)
> : > +		err(EX_IOERR, "get battery info (%d) failed", num);
> : > +
> : > +	if (battio.bst.state != ACPI_BATT_STAT_NOT_PRESENT) {
> : 
> : Prefer positive logic.
> 
> Most common path first is generally the logic I prefer...

I thought there was a PRESENT define but apparently not.

> : > +		printf("State:\t\t\tPresent\n");
> : > +		printf("Rate:\t\t\t%d mWh\n", battio.bst.rate);
> : > +		printf("Cap:\t\t\t%d mWh\n", battio.bst.cap);
> : > +		printf("Volt:\t\t\t%d mV\n", battio.bst.volt);
> : 
> : I agree with these except for a slight misgiving about "cap".  That 
> : information is already exported via sysctl and if we have to export the 
> : same thing different ways, I think the interface is not optimal.
> 
> Capacity isnt' exported via a sysctl.  'life' is, but it doesn't
> export anything more than a percentage.

Life is derived from cap, but like I said above, I'm ok with it.

> : In general, I'd like to move away from acpi-specific ioctls.  There 
> : should be just one way of getting the battery info and it shouldn't 
> : refer to the underlying method names (_BST and _BIF) like the current 
> : ones do.  Mike made a good case for eliminating the dev_t entirely since 
> : there is never any IO for acpi, it's all control traffic.  Sysctl seems 
> : more appropriate for that than creating a device that will never see a 
> : read, write, or other access other than ioctl().  But this is a 
> : complaint about the current design and the half-ioctl, half-sysctl 
> : implementation.
> 
> I'm not entirely sure I agree with a device needing read/write methods
> to be legit.  Especially after I saw sysctl abused for the devinfo
> interface, which likely should have been read instead :-)...

Looking in /dev, nearly all devices support IO.  Only the .ctl or 
.init/.lock devices are questionable.  I think it makes sense for this 
to be a criterion for using a dev_t.

-Nate