Re: Installing DKMS driver on Ubuntu 26.04

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On Thu, 4 Jun 2026 at 22:09, David Gravereaux <[email protected]> wrote:

> ...

Regarding
> /usr/src/linux-gpib-4.3.7/drivers/gpib/tnt4882/tnt4882_gpib.c:63 for
> tnt_paged_readb(), would this be more correct or am I just thinking this
> all wrong?
>
> static inline unsigned int tnt_paged_readb(struct tnt4882_priv *priv,
> unsigned long offset) {
>      unsigned int val;
>
>      // 1. Write the page-in command
>      iowrite8(AUX_PAGEIN, priv->nec7210_priv.mmiobase + AUXMR *
> priv->nec7210_priv.offset);
>
>      // 2. Force full synchronization: Write MUST complete before Read
> starts
>      mb();
>
>      // 3. Read the data from the newly established page
>      val = ioread8(priv->nec7210_priv.mmiobase + offset);
>
>      // 4. Force Read completion before the function returns or next
> instructions run
>      rmb();
>
>      return val;
> }
>
> iowrite8 calls writeb
<https://elixir.bootlin.com/linux/v7.0.10/source/include/asm-generic/io.h#L260>
which
has a barrier before the __raw_writeb same for ioread8
This driver has been working fine without the mb()'s

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<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=
=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, 4 Jun 2026 a=
t 22:09, David Gravereaux &lt;<a href=3D"mailto:[email protected]" target=
=3D"_blank">[email protected]</a>&gt; wrote:<br></div><blockquote class=3D=
"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(2=
04,204,204);padding-left:1ex">...</blockquote><blockquote class=3D"gmail_qu=
ote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,20=
4);padding-left:1ex">Regarding <br>
/usr/src/linux-gpib-4.3.7/drivers/gpib/tnt4882/tnt4882_gpib.c:63 for <br>
tnt_paged_readb(), would this be more correct or am I just thinking this <b=
r>
all wrong?<br>
<br>
static inline unsigned int tnt_paged_readb(struct tnt4882_priv *priv, <br>
unsigned long offset) {<br>
=C2=A0 =C2=A0 =C2=A0unsigned int val;<br>
<br>
=C2=A0 =C2=A0 =C2=A0// 1. Write the page-in command<br>
=C2=A0 =C2=A0 =C2=A0iowrite8(AUX_PAGEIN, priv-&gt;nec7210_priv.mmiobase + A=
UXMR * <br>
priv-&gt;nec7210_priv.offset);<br>
<br>
=C2=A0 =C2=A0 =C2=A0// 2. Force full synchronization: Write MUST complete b=
efore Read <br>
starts<br>
=C2=A0 =C2=A0 =C2=A0mb();<br>
<br>
=C2=A0 =C2=A0 =C2=A0// 3. Read the data from the newly established page<br>
=C2=A0 =C2=A0 =C2=A0val =3D ioread8(priv-&gt;nec7210_priv.mmiobase + offset=
);<br>
<br>
=C2=A0 =C2=A0 =C2=A0// 4. Force Read completion before the function returns=
 or next <br>
instructions run<br>
=C2=A0 =C2=A0 =C2=A0rmb();<br>
<br>
=C2=A0 =C2=A0 =C2=A0return val;<br>
}<br><br></blockquote><div>iowrite8 calls=C2=A0<a href=3D"https://elixir.bo=
otlin.com/linux/v7.0.10/source/include/asm-generic/io.h#L260" target=3D"_bl=
ank">writeb</a>=C2=A0which has a barrier before the __raw_writeb same for i=
oread8</div><div>This driver has been working fine without the mb()&#39;s</=
div><div><br></div></div></div>
</div>

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