Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757316AbaKTJm7 (ORCPT ); Thu, 20 Nov 2014 04:42:59 -0500 Received: from down.free-electrons.com ([37.187.137.238]:45368 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756009AbaKTJm5 (ORCPT ); Thu, 20 Nov 2014 04:42:57 -0500 Date: Thu, 20 Nov 2014 10:42:53 +0100 From: Boris Brezillon To: Brian Norris Cc: David Woodhouse , linux-mtd@lists.infradead.org, Huang Shijie , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Mike Voytovich , Roy Lee Subject: Re: [PATCH v4 2/4] mtd: nand: gpmi: add gpmi_move_bits function Message-ID: <20141120104253.23b543d8@bbrezillon> In-Reply-To: <20141120092209.GD3212@norris-Latitude-E6410> References: <1413794777-32220-1-git-send-email-boris.brezillon@free-electrons.com> <1413794777-32220-3-git-send-email-boris.brezillon@free-electrons.com> <20141120092209.GD3212@norris-Latitude-E6410> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/