WRITTING OPERATION IN CHAR DRIVER

int devwrite(struct file *filep,const char __user *buffer,size_t size,loff_t *llseek)

 82 {

 83

 84     struct Sculldev *lsculldev;

 85     struct Scullqset *lscullqset;

 86     int noqset=0,ret=0,i=0;//noqset=no. of scullqset or qset array bcz no. of scullqset will be sa    me as no. of qset array

 87     int noctw=size,nocsw=0;//noctw=no. of characters to write nocsw=no.of characters sucessfully w    ritten

 88  //   printk(KERN_INFO"TTTTTTTTTsizeTTTTTTTTTTTT=%d\n",size);

 89     printk(KERN_INFO"TTTTTTTTTnoctwTTTTTTTTTTTT=%d\n",noctw);

 90     //int datasize=DATASIZE;

 91     lsculldev=filep->private_data;//take base address of device from private data of struct file

 92     printk(KERN_INFO "lsculldev in write fun_____________=%p",lsculldev);

 93     printk(KERN_INFO"buffer________________=%s\n",buffer);//in application characters written in fd will come to this buffer

 94     printk(KERN_INFO"qsetsize=%d\n",qsetsize);

 95     printk(KERN_INFO"quantumsize=%d\n",quantumsize);

 96

 97     noqset=size/(qsetsize*q if(size%(qsetsize*quantumsize)!=0)

100     {

101         noqset++;//if there is remainder left...it will represent left n. of characters that has t    o be write at last...so one more quantum should be required ..

102     }

103     lsculldev->scullqset=lscullqset=create_scullqset(noqset);//scullqset are being created

104     if(!lsculldev->scullqset)

105     {

106         printk(KERN_INFO"mem not returnd for create_scullqset\n");

107         goto OUT;

108     }

109     printk(KERN_INFO"#############lscullqset###########=%p\n",lscullqset);

110     printk(KERN_INFO"############lscullqset->scullqset########333=%p\n",lscullqset->next);

111     ret=create_qset(lscullqset,noqset);//create array of pointers

112     if(ret<0)

113     {

114         printk(KERN_INFO"error in calling create_qset\n");

115     }

116

117 while(noctw) //check if there is no. of characters to write..if there is...then in the loop

118 {

119 //for(lv=0;lv<noqset;lv++)//this or while satement

120     for(i=0;i<quantumsize;i++)//quantumsize=8...so data will be written in 8 quantums turn by turn

121     {

122 if(noctw>quantumsize)

        noctw=quantumsize;

124 ret=create_quantum(lscullqset,i);//i m creating quantum on write time ..i may calculate no. of qua    antums by using no. of quantums=size/8;

125 if(ret<0)

126 {

127     printk(KERN_INFO"mem is not allocated for quantum\n");

128     goto OUT;

129 }

130 //lscullqset->data[i]=kmalloc(quantumsize,GFP_KERNEL);

131

132 ret=copy_from_user(lscullqset->data[i],buffer+nocsw,noctw);//copy data into each quantum turn by t    urn & increment the pointer so that next data may be written ..not same data frm starting

133 printk(KERN_INFO"ret=%d\n",ret);

134 printk(KERN_INFO"HIIIIIIIbuffer=====%s\n",buffer+nocsw);//print data written in quantums ..io may p    rint whole data bcz it could not get null...so issue of that

135 nocsw=nocsw+(noctw);//cal. no. of characters succesfully written

136 noctw=size-(nocsw-ret);//cal. no. of characters to write

137 printk(KERN_INFO"noctw=%d\n",noctw);

138 }

139 if(i==7 && lscullqset->next)//array of pointers pointing 0 to 7 quantums ..now scullqset is to be     changed

140 {

141     lscullqset=lscullqset->next;

142     i=0;//i again 0

   }

144

145 }

146

147     return 0;

148 OUT:

149     return -1;

150 }

151

-- INSERT --                                                                        151,1         Bot

 int create_qset(struct Scullqset *lscullqset,int noqset)

 25 {

 26 int lv;

 27 for(lv=0;lv<noqset;lv++)//scullqset->data & scullqset->next ...data contains array of pointers..vo    id** data represents pointer to a pointer which is holding quantum address..

 28 {

 29     lscullqset->data=(void*)kmalloc(sizeof(void*)*qsetsize,GFP_KERNEL);

 30     if(!lscullqset->data)

 31     {

 32         printk(KERN_INFO"memory not present for qset array\n");

 33             goto OUT;

 34     }

 35     printk(KERN_INFO"aaaaaaaaaaaaaaaaaaaaaaalscullqset->next=aaaaaaaaaaaa%p\n",lscullqset);

 36   // memset(lscullqset->data,'\0',sizeof(void*)*qsetsize);

 37     lscullqset=lscullqset->next;

 38

 39 }

 40

 41

 42     return 0;

 43 OUT:

 44 printk(KERN_INFO "error in memory allocation\n");

 45     return -1;

 46 }

-- INSERT --