On Tue, Apr 14, 2020 at 04:12:14PM +0300, Dan Carpenter wrote:
> On Mon, Apr 13, 2020 at 04:02:09PM +0200, Oscar Carter wrote:
> > diff --git a/drivers/staging/vt6656/rf.c b/drivers/staging/vt6656/rf.c
> > index 4f9aba0f21b0..3b200d7290a5 100644
> > --- a/drivers/staging/vt6656/rf.c
> > +++ b/drivers/staging/vt6656/rf.c
> > @@ -575,28 +575,14 @@ int vnt_rf_setpower(struct vnt_private *priv, u32 rate, u32 channel)
> >
> > static u8 vnt_rf_addpower(struct vnt_private *priv)
> > {
> > + s32 base;
>
> Just use "int". s32 is for when signed 32 bit is specified in the
> hardware. I realize that it's done in this file, but if all your
> friends jumped off a bridge doesn't mean you should drink their kool-aid.
Ok, lesson learned and thanks for the aclaration about when use every type.
> > s32 rssi = -priv->current_rssi;
> >
> > if (!rssi)
> > return 7;
> >
> > - if (priv->rf_type == RF_VT3226D0) {
> > - if (rssi < -70)
> > - return 9;
> > - else if (rssi < -65)
> > - return 7;
> > - else if (rssi < -60)
> > - return 5;
> > - } else {
> > - if (rssi < -80)
> > - return 9;
> > - else if (rssi < -75)
> > - return 7;
> > - else if (rssi < -70)
> > - return 5;
> > - }
> > -
> > - return 0;
> > + base = (priv->rf_type == RF_VT3226D0) ? -60 : -70;
> > + return (rssi < base--) ? ((rssi - base) / -5) * 2 + 5 : 0;
> ^^^^^^
> I quite hate this postop. It would have been cleaner to write it like:
>
> return (rssi < base) ? ((rssi - (base - 1)) / -5) * 2 + 5 : 0
^ ^
Now, if we apply the minus operator one parentheses can be removed. The
same expression is now:
return (rssi < base) ? ((rssi - base + 1) / -5) * 2 + 5 : 0
I think it's clear enought.
> I'm sorry, I'm not clever enough to figure out the potential values of
> "rssi".
The IEEE 802.11 standard specifies that RSSI can be on a scale of 0 to
up to 255, and that each chipset manufacturer can define their own max
RSSI value. It's all up to the manufacturer.
> How did you work out this formula? It feels like it came from
> a standard or something?
I realized that the two branches of the if statement return the same
values (5, 7, 9) and that each value has a difference of 2 units from
the previous one. Also, every branch has 3 ranges, and every range has
an interval of 5. The only difference in this case is the "base" value
of each branch.
So, the solution was obtain the range index --> (rssi - base) / -5
Then, we need two units for every range index -> * 2
Now, the return value starts with five -------> + 5
The base-- was to obtain the range index the same that the orignal
function.
> Do we not have a function already which implements the standard?
I have been searching but I have not found anything that relates the
RSSI value with the amount of power to add. I have found
struct station_parameters -> member txpwr (struct sta_txpwr type)
but all the functions related to this doesn't set the tx power
depending on the RSSI value.
> regards,
> dan carpenter
>
thanks,
oscar carter
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