From mboxrd@z Thu Jan 1 00:00:00 1970 From: jgunthorpe@obsidianresearch.com (Jason Gunthorpe) Date: Thu, 10 Nov 2016 09:33:15 -0700 Subject: [PATCH fpga 9/9] fpga: Remove support for non-sg drivers In-Reply-To: References: <1478732303-13718-1-git-send-email-jgunthorpe@obsidianresearch.com> <1478732303-13718-10-git-send-email-jgunthorpe@obsidianresearch.com> Message-ID: <20161110163315.GB22004@obsidianresearch.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org > > struct fpga_manager_ops { > > enum fpga_mgr_states (*state)(struct fpga_manager *mgr); > > - int (*write_init)(struct fpga_manager *mgr, u32 flags, > > - const char *buf, size_t count); > > - int (*write)(struct fpga_manager *mgr, const char *buf, size_t count); > > int (*write_init_sg)(struct fpga_manager *mgr, u32 flags, > > struct sg_table *sgt); > > int (*write_sg)(struct fpga_manager *mgr, struct sg_table *sgt); > > @@ -118,6 +113,8 @@ struct fpga_manager { > > > > int fpga_mgr_buf_load(struct fpga_manager *mgr, u32 flags, > > const char *buf, size_t count); > > +int fpga_mgr_buf_load_sg(struct fpga_manager *mgr, u32 flags, > > + struct sg_table *sgt); > > > > int fpga_mgr_firmware_load(struct fpga_manager *mgr, u32 flags, > > const char *image_name); > I don't have any feeling either way about switching to scatter-gather. > (Not zynq or socfpga user) > But I do object to renaming the API. > write_init() and write() do not imply a particular implementation, nor even that > the buffer is coherent. Neither the sg or old linear interface imply any particular underlying driver implementation. All that is being changed is how the list of physical pages gets passed to the driver. The linear interface requires them to be contiguously mapped (eg in a vmap) while the SG interface directly passes a list of physical page addresses. Any alogrithm that works with the old interface can run on the new interface, and the new interface can support much better options for DMA drivers, while not requiring the higher layers to perform a high order allocation (vmap or otherwise) to create the contiguous memory. The reason the old interface is being deleted here is so the fpga mgr API can be expanded to accept a sg list directly. Since we cannot convert a general sg list to linear memory the liner option must be totally removed. > I am working to merge an fpga manager which uses SPI to load the bitstream > (see https://www.spinics.net/lists/arm-kernel/msg539328.html) > Any dma in use there would come from the spi driver. write_init_sg, and write_sg > don't make any sense in my case. No, it still make lots of sense. SPI has been slowly transforming to use the same sort of SG scheme universally, including facing the client. (see 6ad45a27cbe343ec8d7888e5edf6335499a4b555) Some day your driver can just pass the SGs directly to spi and everything will be great. In the mean time it can do sg_miter_next to get mapped buffers. > Would it not make sense to keep the top level API the same? Fundamentally no. Jason