On Fri, Oct 21, 2016 at 10:31:27AM +0200, Laurent Vivier wrote:
>
>
> On 21/10/2016 03:19, David Gibson wrote:
> > ide-test uses many explicit inb() / outb() operations for its IO, which
> > means it's not portable to non-x86 platforms. This cleans it up to use
> > the libqos PCI accessors instead.
> >
> > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> > ---
> > tests/ide-test.c | 179
> > ++++++++++++++++++++++++++++++++++++-------------------
> > 1 file changed, 118 insertions(+), 61 deletions(-)
> >
> > diff --git a/tests/ide-test.c b/tests/ide-test.c
> > index a8a4081..86c4373 100644
> > --- a/tests/ide-test.c
> > +++ b/tests/ide-test.c
> ...
> > @@ -654,7 +700,8 @@ typedef struct Read10CDB {
> > uint16_t padding;
> > } __attribute__((__packed__)) Read10CDB;
> >
> > -static void send_scsi_cdb_read10(uint64_t lba, int nblocks)
> > +static void send_scsi_cdb_read10(QPCIDevice *dev, void *ide_base,
> > + uint64_t lba, int nblocks)
> > {
> > Read10CDB pkt = { .padding = 0 };
> > int i;
> > @@ -670,7 +717,8 @@ static void send_scsi_cdb_read10(uint64_t lba, int
> > nblocks)
> >
> > /* Send Packet */
> > for (i = 0; i < sizeof(Read10CDB)/2; i++) {
> > - outw(IDE_BASE + reg_data, cpu_to_le16(((uint16_t *)&pkt)[i]));
> > + qpci_io_writew(dev, ide_base + reg_data,
> > + le16_to_cpu(((uint16_t *)&pkt)[i]));
> > }
> > }
> >
> ...
> > @@ -780,7 +836,8 @@ static void cdrom_pio_impl(int nblocks)
> >
> > /* HP4: Transfer_Data */
> > for (j = 0; j < MIN((limit / 2), rem); j++) {
> > - rx[offset + j] = le16_to_cpu(inw(IDE_BASE + reg_data));
> > + rx[offset + j] = cpu_to_le16(qpci_io_readw(dev,
> > + ide_base +
> > reg_data));
> > }
> > }
>
> Why do you swap le16_to_cpu() and cpu_to_le16()?
So, obviously le16_to_cpu() and cpu_to_le16() are functionally
identical. But I think my version is conceptually more correct.
This is streaming data via PIO - we're essentially reading a byte
stream in 16-bit chunks. So, overall we want to preserve byte address
order. qpci_io_readw() (and inw()) is designed for reading registers
so it preserves byte significance, rather than address order. So,
since the IDE registers are LE, that means if implicitly contains an
le16_to_cpu(). The cpu_to_le16() undoes that so that rx[] ends up
with the bytestream in the correct order.
> I think this is not semantically correct and the purpose of this patch
> is only to replace inX()/outX() functions.
No, I believe it is correct. And I think the original was technically
wrong, because inw() reads the register in target endian rather than
LE. Of course the only common platform with "real" in/out
instructions is x86, which is LE anyway, so it hardly matters.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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