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6f49a57aa5
Simply, if a client wants any dmaengine channel then prevent all dmaengine modules from being removed. Once the clients are done re-enable module removal. Why?, beyond reducing complication: 1/ Tracking reference counts per-transaction in an efficient manner, as is currently done, requires a complicated scheme to avoid cache-line bouncing effects. 2/ Per-transaction ref-counting gives the false impression that a dma-driver can be gracefully removed ahead of its user (net, md, or dma-slave) 3/ None of the in-tree dma-drivers talk to hot pluggable hardware, but if such an engine were built one day we still would not need to notify clients of remove events. The driver can simply return NULL to a ->prep() request, something that is much easier for a client to handle. Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
44 lines
1.4 KiB
C
44 lines
1.4 KiB
C
/*
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* Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 59
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* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* The full GNU General Public License is included in this distribution in the
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* file called COPYING.
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*/
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#ifndef NETDMA_H
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#define NETDMA_H
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#ifdef CONFIG_NET_DMA
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#include <linux/dmaengine.h>
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#include <linux/skbuff.h>
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static inline struct dma_chan *get_softnet_dma(void)
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{
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struct dma_chan *chan;
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rcu_read_lock();
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chan = rcu_dereference(__get_cpu_var(softnet_data).net_dma);
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rcu_read_unlock();
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return chan;
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}
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int dma_skb_copy_datagram_iovec(struct dma_chan* chan,
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struct sk_buff *skb, int offset, struct iovec *to,
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size_t len, struct dma_pinned_list *pinned_list);
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#endif /* CONFIG_NET_DMA */
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#endif /* NETDMA_H */
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