Re: [PATCH v4 2/4] mtd: nand: gpmi: add gpmi_move_bits function
On Thu, Nov 20, 2014 at 10:42:53AM +0100, Boris Brezillon wrote: > On Thu, 20 Nov 2014 01:22:09 -0800 Brian Norris > wrote: > > On Mon, Oct 20, 2014 at 10:46:15AM +0200, Boris Brezillon wrote: > > > Add a new function to move bits (not bytes) from a memory region to > > > another one. > > > This function is similar to memmove except it acts at bit level. > > > This function is needed to implement GPMI raw access functions, given the > > > fact that ECC engine does not pad ECC bits to the next byte boundary. > > > > > > Signed-off-by: Boris Brezillon > > > --- > > > drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 129 > > > + > > > drivers/mtd/nand/gpmi-nand/gpmi-nand.h | 4 + > > > 2 files changed, 133 insertions(+) > > > > > > diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > > b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > > index 87e658c..5d4f140 100644 > > > --- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > > +++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > > @@ -1353,3 +1353,132 @@ int gpmi_read_page(struct gpmi_nand_data *this, > > > set_dma_type(this, DMA_FOR_READ_ECC_PAGE); > > > return start_dma_with_bch_irq(this, desc); > > > } > > > + > > > +void gpmi_move_bits(u8 *dst, size_t dst_bit_off, > > > + const u8 *src, size_t src_bit_off, > > > + size_t nbits) > > > > Two things: > > > > 1) Yikes! This function is a little hairy. > > Yes I know, and if you see a much simpler algorithm to do that, I'm > really interested :-). No ideas at the moment :) > > 2) This function really deserves a full comment header (kerneldoc?); it > > needs to have clearly-documented high-level semantics. > > I'll add a kernel doc header. > > > > > I'm not sure how to address #1, as the complexity is necessary. Did you > > run this through some unit tests, at least? > > No, but I did test it with several ECC configs. > Anyway, if I develop such unit tests, do you want me to put them in the > driver code (under an #ifdef section) ? I dunno, that seems like it might just clutter the file more, and I'm not sure if anyone is likely to run them. I was mostly curious how you've verified it. Brian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v4 2/4] mtd: nand: gpmi: add gpmi_move_bits function
On Thu, 20 Nov 2014 01:22:09 -0800 Brian Norris wrote: > On Mon, Oct 20, 2014 at 10:46:15AM +0200, Boris Brezillon wrote: > > Add a new function to move bits (not bytes) from a memory region to > > another one. > > This function is similar to memmove except it acts at bit level. > > This function is needed to implement GPMI raw access functions, given the > > fact that ECC engine does not pad ECC bits to the next byte boundary. > > > > Signed-off-by: Boris Brezillon > > --- > > drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 129 > > + > > drivers/mtd/nand/gpmi-nand/gpmi-nand.h | 4 + > > 2 files changed, 133 insertions(+) > > > > diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > index 87e658c..5d4f140 100644 > > --- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > +++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c > > @@ -1353,3 +1353,132 @@ int gpmi_read_page(struct gpmi_nand_data *this, > > set_dma_type(this, DMA_FOR_READ_ECC_PAGE); > > return start_dma_with_bch_irq(this, desc); > > } > > + > > +void gpmi_move_bits(u8 *dst, size_t dst_bit_off, > > + const u8 *src, size_t src_bit_off, > > + size_t nbits) > > Two things: > > 1) Yikes! This function is a little hairy. Yes I know, and if you see a much simpler algorithm to do that, I'm really interested :-). > > 2) This function really deserves a full comment header (kerneldoc?); it > needs to have clearly-documented high-level semantics. I'll add a kernel doc header. > > I'm not sure how to address #1, as the complexity is necessary. Did you > run this through some unit tests, at least? No, but I did test it with several ECC configs. Anyway, if I develop such unit tests, do you want me to put them in the driver code (under an #ifdef section) ? -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v4 2/4] mtd: nand: gpmi: add gpmi_move_bits function
On Mon, Oct 20, 2014 at 10:46:15AM +0200, Boris Brezillon wrote:
> Add a new function to move bits (not bytes) from a memory region to
> another one.
> This function is similar to memmove except it acts at bit level.
> This function is needed to implement GPMI raw access functions, given the
> fact that ECC engine does not pad ECC bits to the next byte boundary.
>
> Signed-off-by: Boris Brezillon
> ---
> drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 129
> +
> drivers/mtd/nand/gpmi-nand/gpmi-nand.h | 4 +
> 2 files changed, 133 insertions(+)
>
> diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
> b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
> index 87e658c..5d4f140 100644
> --- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
> +++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
> @@ -1353,3 +1353,132 @@ int gpmi_read_page(struct gpmi_nand_data *this,
> set_dma_type(this, DMA_FOR_READ_ECC_PAGE);
> return start_dma_with_bch_irq(this, desc);
> }
> +
> +void gpmi_move_bits(u8 *dst, size_t dst_bit_off,
> + const u8 *src, size_t src_bit_off,
> + size_t nbits)
Two things:
1) Yikes! This function is a little hairy.
2) This function really deserves a full comment header (kerneldoc?); it
needs to have clearly-documented high-level semantics.
I'm not sure how to address #1, as the complexity is necessary. Did you
run this through some unit tests, at least?
> +{
[snip]
> +}
Brian
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
