wa-nep.c

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/*
 * WUSB Wire Adapter: Control/Data Streaming Interface (WUSB[8])
 * Notification EndPoint support
 *
 * Copyright (C) 2006 Intel Corporation
 * Inaky Perez-Gonzalez <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 *
 * This part takes care of getting the notification from the hw
 * only and dispatching through wusbwad into
 * wa_notif_dispatch. Handling is done there.
 *
 * WA notifications are limited in size; most of them are three or
 * four bytes long, and the longest is the HWA Device Notification,
 * which would not exceed 38 bytes (DNs are limited in payload to 32
 * bytes plus 3 bytes header (WUSB1.0[7.6p2]), plus 3 bytes HWA
 * header (WUSB1.0[8.5.4.2]).
 *
 * It is not clear if more than one Device Notification can be packed
 * in a HWA Notification, I assume no because of the wording in
 * WUSB1.0[8.5.4.2]. In any case, the bigger any notification could
 * get is 256 bytes (as the bLength field is a byte).
 *
 * So what we do is we have this buffer and read into it; when a
 * notification arrives we schedule work to a specific, single thread
 * workqueue (so notifications are serialized) and copy the
 * notification data. After scheduling the work, we rearm the read from
 * the notification endpoint.
 *
 * Entry points here are:
 *
 * wa_nep_[create|destroy]()   To initialize/release this subsystem
 *
 * wa_nep_cb()                 Callback for the notification
 *                                endpoint; when data is ready, this
 *                                does the dispatching.
 */
#include <linux/workqueue.h>
#include <linux/ctype.h>
#include <linux/slab.h>

#include "wa-hc.h"
#include "wusbhc.h"

/* Structure for queueing notifications to the workqueue */
struct wa_notif_work {
    struct work_struct work;
    struct wahc *wa;
    size_t size;
    u8 data[];
};

/*
 * Process incoming notifications from the WA's Notification EndPoint
 * [the wuswad daemon, basically]
 *
 * @_nw:    Pointer to a descriptor which has the pointer to the
 *      @wa, the size of the buffer and the work queue
 *      structure (so we can free all when done).
 * @returns     0 if ok, < 0 errno code on error.
 *
 * All notifications follow the same format; they need to start with a
 * 'struct wa_notif_hdr' header, so it is easy to parse through
 * them. We just break the buffer in individual notifications (the
 * standard doesn't say if it can be done or is forbidden, so we are
 * cautious) and dispatch each.
 *
 * So the handling layers are is:
 *
 *   WA specific notification (from NEP)
 *      Device Notification Received -> wa_handle_notif_dn()
 *        WUSB Device notification generic handling
 *      BPST Adjustment -> wa_handle_notif_bpst_adj()
 *      ... -> ...
 *
 * @wa has to be referenced
 */
static void wa_notif_dispatch(struct work_struct *ws)
{
    void *itr;
    u8 missing = 0;
    struct wa_notif_work *nw = container_of(ws, struct wa_notif_work, work);
    struct wahc *wa = nw->wa;
    struct wa_notif_hdr *notif_hdr;
    size_t size;

    struct device *dev = &wa->usb_iface->dev;

#if 0
    /* FIXME: need to check for this??? */
    if (usb_hcd->state == HC_STATE_QUIESCING)   /* Going down? */
        goto out;               /* screw it */
#endif
    atomic_dec(&wa->notifs_queued);     /* Throttling ctl */
    dev = &wa->usb_iface->dev;
    size = nw->size;
    itr = nw->data;

    while (size) {
        if (size < sizeof(*notif_hdr)) {
            missing = sizeof(*notif_hdr) - size;
            goto exhausted_buffer;
        }
        notif_hdr = itr;
        if (size < notif_hdr->bLength)
            goto exhausted_buffer;
        itr += notif_hdr->bLength;
        size -= notif_hdr->bLength;
        /* Dispatch the notification [don't use itr or size!] */
        switch (notif_hdr->bNotifyType) {
        case HWA_NOTIF_DN: {
            struct hwa_notif_dn *hwa_dn;
            hwa_dn = container_of(notif_hdr, struct hwa_notif_dn,
                          hdr);
            wusbhc_handle_dn(wa->wusb, hwa_dn->bSourceDeviceAddr,
                     hwa_dn->dndata,
                     notif_hdr->bLength - sizeof(*hwa_dn));
            break;
        }
        case WA_NOTIF_TRANSFER:
            wa_handle_notif_xfer(wa, notif_hdr);
            break;
        case DWA_NOTIF_RWAKE:
        case DWA_NOTIF_PORTSTATUS:
        case HWA_NOTIF_BPST_ADJ:
            /* FIXME: unimplemented WA NOTIFs */
            /* fallthru */
        default:
            dev_err(dev, "HWA: unknown notification 0x%x, "
                "%zu bytes; discarding\n",
                notif_hdr->bNotifyType,
                (size_t)notif_hdr->bLength);
            break;
        }
    }
out:
    wa_put(wa);
    kfree(nw);
    return;

    /* THIS SHOULD NOT HAPPEN
     *
     * Buffer exahusted with partial data remaining; just warn and
     * discard the data, as this should not happen.
     */
exhausted_buffer:
    dev_warn(dev, "HWA: device sent short notification, "
         "%d bytes missing; discarding %d bytes.\n",
         missing, (int)size);
    goto out;
}

/*
 * Deliver incoming WA notifications to the wusbwa workqueue
 *
 * @wa: Pointer the Wire Adapter Controller Data Streaming
 *              instance (part of an 'struct usb_hcd').
 * @size:       Size of the received buffer
 * @returns     0 if ok, < 0 errno code on error.
 *
 * The input buffer is @wa->nep_buffer, with @size bytes
 * (guaranteed to fit in the allocated space,
 * @wa->nep_buffer_size).
 */
static int wa_nep_queue(struct wahc *wa, size_t size)
{
    int result = 0;
    struct device *dev = &wa->usb_iface->dev;
    struct wa_notif_work *nw;

    /* dev_fnstart(dev, "(wa %p, size %zu)\n", wa, size); */
    BUG_ON(size > wa->nep_buffer_size);
    if (size == 0)
        goto out;
    if (atomic_read(&wa->notifs_queued) > 200) {
        if (printk_ratelimit())
            dev_err(dev, "Too many notifications queued, "
                "throttling back\n");
        goto out;
    }
    nw = kzalloc(sizeof(*nw) + size, GFP_ATOMIC);
    if (nw == NULL) {
        if (printk_ratelimit())
            dev_err(dev, "No memory to queue notification\n");
        goto out;
    }
    INIT_WORK(&nw->work, wa_notif_dispatch);
    nw->wa = wa_get(wa);
    nw->size = size;
    memcpy(nw->data, wa->nep_buffer, size);
    atomic_inc(&wa->notifs_queued);     /* Throttling ctl */
    queue_work(wusbd, &nw->work);
out:
    /* dev_fnend(dev, "(wa %p, size %zu) = result\n", wa, size, result); */
    return result;
}

/*
 * Callback for the notification event endpoint
 *
 * Check's that everything is fine and then passes the data to be
 * queued to the workqueue.
 */
static void wa_nep_cb(struct urb *urb)
{
    int result;
    struct wahc *wa = urb->context;
    struct device *dev = &wa->usb_iface->dev;

    switch (result = urb->status) {
    case 0:
        result = wa_nep_queue(wa, urb->actual_length);
        if (result < 0)
            dev_err(dev, "NEP: unable to process notification(s): "
                "%d\n", result);
        break;
    case -ECONNRESET:   /* Not an error, but a controlled situation; */
    case -ENOENT:       /* (we killed the URB)...so, no broadcast */
    case -ESHUTDOWN:
        dev_dbg(dev, "NEP: going down %d\n", urb->status);
        goto out;
    default:    /* On general errors, we retry unless it gets ugly */
        if (edc_inc(&wa->nep_edc, EDC_MAX_ERRORS,
                EDC_ERROR_TIMEFRAME)) {
            dev_err(dev, "NEP: URB max acceptable errors "
                "exceeded, resetting device\n");
            wa_reset_all(wa);
            goto out;
        }
        dev_err(dev, "NEP: URB error %d\n", urb->status);
    }
    result = wa_nep_arm(wa, GFP_ATOMIC);
    if (result < 0) {
        dev_err(dev, "NEP: cannot submit URB: %d\n", result);
        wa_reset_all(wa);
    }
out:
    return;
}

/*
 * Initialize @wa's notification and event's endpoint stuff
 *
 * This includes the allocating the read buffer, the context ID
 * allocation bitmap, the URB and submitting the URB.
 */
int wa_nep_create(struct wahc *wa, struct usb_interface *iface)
{
    int result;
    struct usb_endpoint_descriptor *epd;
    struct usb_device *usb_dev = interface_to_usbdev(iface);
    struct device *dev = &iface->dev;

    edc_init(&wa->nep_edc);
    epd = &iface->cur_altsetting->endpoint[0].desc;
    wa->nep_buffer_size = 1024;
    wa->nep_buffer = kmalloc(wa->nep_buffer_size, GFP_KERNEL);
    if (wa->nep_buffer == NULL) {
        dev_err(dev, "Unable to allocate notification's read buffer\n");
        goto error_nep_buffer;
    }
    wa->nep_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (wa->nep_urb == NULL) {
        dev_err(dev, "Unable to allocate notification URB\n");
        goto error_urb_alloc;
    }
    usb_fill_int_urb(wa->nep_urb, usb_dev,
             usb_rcvintpipe(usb_dev, epd->bEndpointAddress),
             wa->nep_buffer, wa->nep_buffer_size,
             wa_nep_cb, wa, epd->bInterval);
    result = wa_nep_arm(wa, GFP_KERNEL);
    if (result < 0) {
        dev_err(dev, "Cannot submit notification URB: %d\n", result);
        goto error_nep_arm;
    }
    return 0;

error_nep_arm:
    usb_free_urb(wa->nep_urb);
error_urb_alloc:
    kfree(wa->nep_buffer);
error_nep_buffer:
    return -ENOMEM;
}

void wa_nep_destroy(struct wahc *wa)
{
    wa_nep_disarm(wa);
    usb_free_urb(wa->nep_urb);
    kfree(wa->nep_buffer);
}