Date: Wed, 20 Feb 2013 07:15:47 -0700 From: Warner Losh <imp@bsdimp.com> To: Aleksandr Rybalko <ray@freebsd.org> Cc: freebsd-arm@freebsd.org, freebsd-mips@freebsd.org Subject: Re: SPI, _sz fields in struct spi_command Message-ID: <54C08D8E-4C5F-49AF-BEE6-D78EC05D2A24@bsdimp.com> In-Reply-To: <20130220142140.f8e5a616c75d72e2519dbc69@freebsd.org> References: <20130220142140.f8e5a616c75d72e2519dbc69@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Feb 20, 2013, at 5:21 AM, Aleksandr Rybalko wrote:
> Hello ARM and MIPS hackers!
>=20
> Sorry for cross-post, but we have supported SPI devices on both
> platforms (and seems no others).
>=20
> Anyone know any reasons to keep both TX and RX _sz fields with same
> values?
I wrote them to be separate for a reason.... I think I'd thought =
there'd be cases when you'd want to throw away the results or transmit =
garbage... I can't think of why right now...
> sys/dev/flash/at45d.c
> static int
> at45d_get_mfg_info(device_t dev, uint8_t *resp)
> {
> ...
> cmd.tx_cmd_sz =3D cmd.rx_cmd_sz =3D 5;
> ...
> }
>=20
> or sys/dev/flash/mx25l.c
> static int
> mx25l_read(device_t dev, off_t offset, caddr_t data, off_t count)
> {
> ...
> cmd.tx_cmd_sz =3D 5;
> cmd.rx_cmd_sz =3D 5;
> ...
> }
>=20
> That always require second but unused buffer or writable tx buffer. =
And
> not all controllers able to TX with RX same time. (at least rt305x
> can't). So if nobody have any objections, I will update drivers (SPI
> controllers and SPI attached devices) to set unused _sz field to zero.
> IIRC, I will require help with AT91 controller update, at least with
> testing.
The AT91, I think, required a minimum size, which is why the at45d =
driver set it I think..
I can't imagine an SPI controller that can't do both, because when you =
write something with SPI, you usually have to read back the status at =
the same time...
Warner
> Thanks.
>=20
> WBW
> --=20
> Aleksandr Rybalko <ray@freebsd.org>
> _______________________________________________
> freebsd-mips@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-mips
> To unsubscribe, send any mail to =
"freebsd-mips-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?54C08D8E-4C5F-49AF-BEE6-D78EC05D2A24>