diff options
Diffstat (limited to 'drivers/usb/storage/protocol.c')
| -rw-r--r-- | drivers/usb/storage/protocol.c | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c new file mode 100644 index 0000000000..9033e505db --- /dev/null +++ b/drivers/usb/storage/protocol.c @@ -0,0 +1,181 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Driver for USB Mass Storage compliant devices + * + * Current development and maintenance by: + * (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net) + * + * Developed with the assistance of: + * (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org) + * (c) 2002 Alan Stern (stern@rowland.org) + * + * Initial work by: + * (c) 1999 Michael Gee (michael@linuxspecific.com) + * + * This driver is based on the 'USB Mass Storage Class' document. This + * describes in detail the protocol used to communicate with such + * devices. Clearly, the designers had SCSI and ATAPI commands in + * mind when they created this document. The commands are all very + * similar to commands in the SCSI-II and ATAPI specifications. + * + * It is important to note that in a number of cases this class + * exhibits class-specific exemptions from the USB specification. + * Notably the usage of NAK, STALL and ACK differs from the norm, in + * that they are used to communicate wait, failed and OK on commands. + * + * Also, for certain devices, the interrupt endpoint is used to convey + * status of a command. + */ + +#include <linux/highmem.h> +#include <linux/export.h> +#include <scsi/scsi.h> +#include <scsi/scsi_cmnd.h> + +#include "usb.h" +#include "protocol.h" +#include "debug.h" +#include "scsiglue.h" +#include "transport.h" + +/*********************************************************************** + * Protocol routines + ***********************************************************************/ + +void usb_stor_pad12_command(struct scsi_cmnd *srb, struct us_data *us) +{ + /* + * Pad the SCSI command with zeros out to 12 bytes. If the + * command already is 12 bytes or longer, leave it alone. + * + * NOTE: This only works because a scsi_cmnd struct field contains + * a unsigned char cmnd[16], so we know we have storage available + */ + for (; srb->cmd_len < 12; srb->cmd_len++) + srb->cmnd[srb->cmd_len] = 0; + + /* send the command to the transport layer */ + usb_stor_invoke_transport(srb, us); +} + +void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us) +{ + /* + * fix some commands -- this is a form of mode translation + * UFI devices only accept 12 byte long commands + * + * NOTE: This only works because a scsi_cmnd struct field contains + * a unsigned char cmnd[16], so we know we have storage available + */ + + /* Pad the ATAPI command with zeros */ + for (; srb->cmd_len < 12; srb->cmd_len++) + srb->cmnd[srb->cmd_len] = 0; + + /* set command length to 12 bytes (this affects the transport layer) */ + srb->cmd_len = 12; + + /* XXX We should be constantly re-evaluating the need for these */ + + /* determine the correct data length for these commands */ + switch (srb->cmnd[0]) { + + /* for INQUIRY, UFI devices only ever return 36 bytes */ + case INQUIRY: + srb->cmnd[4] = 36; + break; + + /* again, for MODE_SENSE_10, we get the minimum (8) */ + case MODE_SENSE_10: + srb->cmnd[7] = 0; + srb->cmnd[8] = 8; + break; + + /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */ + case REQUEST_SENSE: + srb->cmnd[4] = 18; + break; + } /* end switch on cmnd[0] */ + + /* send the command to the transport layer */ + usb_stor_invoke_transport(srb, us); +} + +void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb, + struct us_data *us) +{ + /* send the command to the transport layer */ + usb_stor_invoke_transport(srb, us); +} +EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command); + +/*********************************************************************** + * Scatter-gather transfer buffer access routines + ***********************************************************************/ + +/* + * Copy a buffer of length buflen to/from the srb's transfer buffer. + * Update the **sgptr and *offset variables so that the next copy will + * pick up from where this one left off. + */ +unsigned int usb_stor_access_xfer_buf(unsigned char *buffer, + unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr, + unsigned int *offset, enum xfer_buf_dir dir) +{ + unsigned int cnt = 0; + struct scatterlist *sg = *sgptr; + struct sg_mapping_iter miter; + unsigned int nents = scsi_sg_count(srb); + + if (sg) + nents = sg_nents(sg); + else + sg = scsi_sglist(srb); + + sg_miter_start(&miter, sg, nents, dir == FROM_XFER_BUF ? + SG_MITER_FROM_SG: SG_MITER_TO_SG); + + if (!sg_miter_skip(&miter, *offset)) + return cnt; + + while (sg_miter_next(&miter) && cnt < buflen) { + unsigned int len = min_t(unsigned int, miter.length, + buflen - cnt); + + if (dir == FROM_XFER_BUF) + memcpy(buffer + cnt, miter.addr, len); + else + memcpy(miter.addr, buffer + cnt, len); + + if (*offset + len < miter.piter.sg->length) { + *offset += len; + *sgptr = miter.piter.sg; + } else { + *offset = 0; + *sgptr = sg_next(miter.piter.sg); + } + cnt += len; + } + sg_miter_stop(&miter); + + return cnt; +} +EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf); + +/* + * Store the contents of buffer into srb's transfer buffer and set the + * SCSI residue. + */ +void usb_stor_set_xfer_buf(unsigned char *buffer, + unsigned int buflen, struct scsi_cmnd *srb) +{ + unsigned int offset = 0; + struct scatterlist *sg = NULL; + + buflen = min(buflen, scsi_bufflen(srb)); + buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset, + TO_XFER_BUF); + if (buflen < scsi_bufflen(srb)) + scsi_set_resid(srb, scsi_bufflen(srb) - buflen); +} +EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf); |